Device for measuring physical quantity using pulsed laser interferometry

ABSTRACT

Pulsed laser beams are applied to an object to be measured. A first laser beam of a pulsed laser beam having a first wavelength which is oscillated immediately after the rise of the pulsed laser beam, and a second laser beam having a second wavelength which is oscillated thereafter are used. Based on a difference between an intensity of first interfered light of reflected light of the first laser beam or transmitted light thereof, and an intensity of reflected light of the second laser beam or transmitted light thereof, temperatures of the object to be measured, and whether the temperatures are on increase or on decrease are judged. The method and device can be realized by simple structures and can measure a direction of changes of the physical quantities.

This application is a divisional application filed under 37 CFR §1.53(b)of parent application Ser. No. 08/401,689, filed Mar. 10, 1995, now U.S.Pat. No. 5,773,316.

BACKGROUND OF THE INVENTION

The present invention relates to a method and a device for measuring aphysical quantity of an object to be measured by applying laser beams tothe object, more specifically to a method and a device for measuring atemperature of a semiconductor substrate without making physical contactwith it, by the use of laser beams. Further, the present inventionrelates to a method and a device for measuring light wavelengths, morespecifically to a method and a device for measuring light wavelengthshifts occurring in a short period of time.

Currently, semiconductor device fabrication processes and designcharacteristics of semiconductor devices rely heavily on temperaturecontrol. Yet, delicate fabrication processes do not allow semiconductorsubstrates to be contacted by any sort of temperature measuring probe,etc. Hence, it is required to accurately measure the temperature ofsemiconductor substrates without contact.

As a temperature measuring device for such noncontact temperaturemeasurement of semiconductor substrates, a device is known which usesthe fact that the light transmittance of a semiconductor substratedecreases with increases of its temperature (see Japanese PatentLaid-Open Publication No. 271127/1988, Japanese Patent Laid-OpenPublication No. 79339/1988, and Japanese Patent Laid-Open PublicationNo. 216526/1991, etc.).

Japanese Patent Laid-Open Publication No. 96247/1991 discloses a methodfor such noncontact temperature measurement of a semiconductor substrateto be measured which uses the fact that the intensity of a interferedlight beam reflected from either the top or bottom surfaces of asemiconductor substrate varies depending on the temperature of thesubstrate. With changes in the temperature of the semiconductorsubstrate, the dielectric constant of the substrate changes as thesubstrate expands, altering its thickness, whereby variations in theintensity of the interfered light reflected therefrom can be used tomeasure the change in temperature of the substrate.

But, the temperature measuring method disclosed in Japanese PatentLaid-Open Publication No. 96247/1991 cannot determine whether or not thetemperature is rising or falling.

A temperature measuring device which is based on the same principle asthe temperature measuring method disclosed in Japanese Patent Laid-OpenPublication No. 96247/1991 but which can measure the direction oftemperature change has been proposed. See K. L. Saenger, et al.,“Wavelength-Modulated Interformetric Thermometry for Improved SubstrateTemperature Measurement”, Rev. Sci. Instrum., Vol. 63, No. 8, pp.3862-3868, Aug. 1992.

The temperature measuring device described in the above reference usesan approximately 1.5 μm-oscillation wavelength semiconductor laser. Thislaser emits coherent laser beams which have been wavelength-modulated byan alternating current injected into the semiconductor laser, and thelaser beams are applied to a semiconductor substrate to be measured.Interfered light of the reflected light from the substrate is detectedby a photo-detecting element and converted to detected signals, and thedetected signals are wavelength-differentiated by a lock-in amplifier.Based on processing of the differentiated and non-differentiateddetected signals, it is determined whether the substrate temperature isrising or falling.

Currently, in the optical measurement field it is required to accuratelymeasure light wavelength shifts taking place in a short period of time.Such accurate optical measurement is necessary especially to accuratelymeasure stability of oscillation wavelengths of laser beams and amountsof wavelength shift amounts, and to measure accurately wavelength shiftsof laser beams as they undergo rising and falling.

In the conventional wavelength measuring methods it has been generallyknown that light to be measured is spectrally diffracted byspectroscopes or optical spectrum analyzers for the measurement ofwavelengths of the light to be measured. That is, in these methods,light to be measured is spectrally diffracted to measure spectralwavelengths, whereby wavelengths of the light to be measured aremeasured.

Thus, the conventional temperature measuring devices must include alarge number of instruments and devices, such as the laser modulatingmeans, the lock-in amplifier, etc., which makes the structure of suchdevices complicated and their costs high. This is a disadvantage. Foraccurate measurement of abrupt temperature changes, e.g. more than 100°C. per minute, instruments and devices which are operative at higherspeeds are required, which adds further to the cost. This is also adisadvantage. Finally, conventional temperature measuring devices canmeasure the direction of temperature changes only when a waveform ofinterfered light crosses an average value, which makes precisetemperature measurement impossible.

The temperature measuring device described in the reference aboveincludes as a light source a semiconductor laser of a III-V compoundsemiconductor. Its oscillation wavelength is approximately 1.6 μm atmost. In the case where light of such relatively short wavelength (λ) isused, the measurable temperature ranges for various semiconductorsubstrates, such as silicon, GaAs, or others with relatively narrowenergy band gaps, are small. This is because the energy band gaps ofsuch semiconductors narrows as their temperatures rise. As a result,their absorption of laser beam light becomes larger. For example, asilicon wafer has a 1.12 eV energy band gap and absorbs laser light ofapproximately 1.6 μm wavelength when the measurement temperature reaches750° C.

Furthermore, the temperature measuring device described in the referenceabove performs temperature measurement based on periodic variations inthe intensities of interfered light reflected from the semiconductorsubstrate. Accordingly, the temperature cannot be substantially measureduntil the intensities of the interfered light varies through at leastone period; maximum and minimum intensity values being given. Thus it isanother disadvantage that temperature measurement cannot be conductedwithout changing temperatures until maximum and minimum intensity valuesof the interfered light employed are given.

It is also a disadvantage of the temperature measuring device describedin the reference above that in the case where an object to be measuredis a semiconductor substrate, such as silicon, GaAs or others, laserbeams are adversely absorbed by the semiconductor substrate as itstemperature rises, and the resulting temperature measurement is notaccurate.

But according to the conventional wavelength measuring method usingspectral diffraction, it is necessary to scan a required wavelength bandfor one wavelength measuring operation. Such method has found itdifficult to measure wavelength shifts occurring in a period of somemsec-scanning time.

In addition, according to the conventional wavelength measuring methodusing spectral diffraction, to improve accuracy of measuringwavelengths, it is necessary to elongate an optical path of light to bemeasured along which the light to be measured follow. Disadvantageouslythe wavelength measuring device for such method is accordinglylarge-sized.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a device for measuringphysical quantities has a simple structure, and a method for measuringphysical quantities which can precisely measure the direction of changethereof.

Another object of the present invention is to provide a device formeasuring a temperature which has a simple structure, and a method formeasuring a temperature which can precisely measure the direction ofchange thereof.

Still another object of the present invention is to provide a method anda device for measuring a temperature which can measure a wide range oftemperatures.

Still another object of the present invention is to provide a method anda device for measuring a temperature which can measure a temperatureimmediately after the start of measuring the intensities of interferedlight.

Still another object of the present invention is to provide a method anda device for measuring a temperature which can measure a temperature ofa semiconductor substrate up to high temperatures.

Still another object of the present invention is to provide a method anda device for measuring wavelengths which can measure quickly shiftingwavelengths without allocating a scanning time for the spectraldiffraction.

The above-described object of the present invention is achieved by ameasuring method for irradiating laser beams to an object to be measuredto measure a physical quantity of the object to be measured, pulsedlaser beams being irradiated to the object to be measured, first laserbeams of a first wavelength of the pulsed laser beams and second laserbeams of a second wavelength thereof being used to measure the physicalquantity of the object, the first wavelength being oscillated afterrises of the pulsed laser beams, the second wavelength being oscillatedthereafter.

In the above-described measuring method, it is preferable thattemperatures of the object are measured, based on changes of intensitiesof first interfered light of reflected light or transmitted light of oneof the first laser beams on or by the object, and changes of intensitiesof second interfered light of reflected light or transmitted light ofone of the second laser beams on or by the object.

In the above-described measuring method, it is preferable that thetemperatures of the object are judged to be on the increase or decrease,based on a direction of the changes of intensities of the first or thesecond interfered light and on a difference between the intensity of thefirst interfered light and that of the second interfered light.

In the above-described measuring method, it is preferable that themeasuring method measures the physical quantity, temperatures, or adirection of changes of temperatures of the object to be measured, byusing a semiconductor laser having a characteristic that the firstwavelength of the first laser beams is shorter than the secondwavelength of the second laser beams.

In the above-described measuring method, it is preferable that thetemperatures of the object are determined to be on an increase when theintensities of the first interfered light are higher than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on anincrease, the temperatures of the objects are judged to be on decreasewhen the intensities of the first interfered light are lower than thoseof the second interfered light at the time that the intensities of thefirst interfered light or those of the second interfered light are onthe increase, the temperatures of the object are judged to be on thedecrease when the intensities of the first interfered light are higherthan those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on the decrease, the temperatures of the objectsare judged to be on the increase when the intensities of the firstinterfered light are lower than those of the second interfered light atthe time that the intensities of the first interfered light or those ofthe second interfered light are on the decrease.

In the above-described measuring method, it is preferable that themeasuring method measures the physical quantity, temperatures, or adirection of changes of temperatures of the object to be measured byusing a semiconductor laser having a characteristic that the firstwavelength of the first laser beams is longer than the second wavelengthof the second laser beams.

In the above-described measuring method, it is preferable that thetemperatures of the object are judged to be on the decrease when theintensities of the first interfered light are higher than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on theincrease, the temperatures of the objects are judged to be ontheincrease when the intensities of the first interfered light are lowerthan those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on the increase, the temperatures of the object arejudged to be on the increase when the intensities of the firstinterfered light are higher than those of the second interfered light atthe time that the intensities of the first interfered light or those ofthe second interfered light are on the decrease, the temperatures of theobjects are judged to be on the decrease when the intensities of thefirst interfered light are lower than those of the second interferedlight at the time that the intensities of the first interfered light orthose of the second interfered light are on the decrease.

In the above-described measuring method, it is preferable that when thesecond wavelength of the second interfered light is represented by λ, athickness of the object to be measured is represented by d, and arefractive index of the object to be measured is represented by n, adifference Δλ between the first wavelength of the first interfered lightand the second wavelength of the second interfered light satisfies

|Δλ|<λ²/(2nd+λ)

In the above-described measuring method, it is preferable that the firstlaser beams are oscillated within approximately 0.5 msec after rises ofthe pulsed laser beams.

The above-described object of the present invention is achieved by ameasuring method for irradiating a laser beam of coherence to an objectto be measured to measure change amounts of temperatures of the objectto be measured, based on intensities of reflected light or interferedlight on or by the object, the method comprising: a predicting step of,before a temperature measuring operation, predicting a maximum value anda minimum value of the intensities of the interfered light; and ameasuring step of measuring the change amounts of the temperatures ofthe object, based on the intensities of the interfered light, and thepredicted maximum and minimum values.

In the above-described measuring method, it is preferable that theincident angle in the predicting step is so changed that the maximum andthe minimum values of the intensities of the interfered light are givenat least in one set.

In the above-described measuring method, it is preferable that when awavelength of the light of coherence to be irradiated is represented byλ, an incident angle is represented by θ, a thickness of the object tobe measured is represented by d, and a refractive index thereof isrepresented by n, an angle change Δθ of the incident angle in thepredicting step satisfies a formula

Δθ≧sin⁻¹ [n ²−{(n ²−sin²θ)^(½)−λ/4d} ²]^(½)−θ.

In the above-described measuring method, it is preferable thatoscillating intensities of the laser beams to be irradiated to theobject to be measured are changed based on temperatures of the object tobe measured.

In the above-described measuring method, it is preferable thatintensities of the laser beams to be irradiated to the object to bemeasured are constant or increased when the temperature of the object isrising, and intensities of the laser beams are constant or decreasedwhen the temperature is falling.

In the above-described measuring method, it is preferable that theintensities of the laser beams to be irradiated to the object to bemeasured are decreased based on the temperature of the object to bemeasured.

In the above-described measuring method, it is preferable that one orplural optical windows are provided in a measuring light path, at leastone surface of the optical windows are slanted with respect to theoptical axis of the laser beams so that no interference of reflectedlight inside each of the optical windows and between the optical windowstakes place.

The above-described object of the present invention is achieved by ameasuring device for irradiating laser beams to an object to be measuredto measure a physical quantity of the object, the device comprising:irradiating means which oscillates pulsed laser beams to irradiate firstlaser beams of a first wavelength which are oscillated after rises ofthe pulsed laser beams, and second laser beams which are oscillatedthereafter and differs from the first wavelength; and measuring meanswhich measures the physical quantity of the object to be measured by theuse of the first laser beams and the second laser beams irradiated bythe irradiating means.

In the above-described measuring device, it is preferable that themeasuring means measures temperatures of the object to be measured,based on changes of intensities of first interfered light of reflectedlight or transmitted light of one of the first laser beams on or by theobject, or changes of intensities of second interfered light ofreflected light or transmitted light of one of the second laser beams onor by the object.

In the above-described measuring device, it is preferable that themeasuring means judges that the temperatures of the object are judged tobe on the increase or decrease, based on a direction of the changes ofintensities of the first or the second interfered light and on adifference between the intensity of the first interfered light and thatof the second interfered light.

In the above-described measuring device, it is preferable that theirradiating means includes a semiconductor laser having a characteristicthat the first wavelength of the first laser beams is shorter than thesecond wavelength of the second laser beams, and the measuring devicemeasures the physical quantity, a temperature, or a direction of changesof a temperature of the object to be measured.

In the above-described measuring device, it is preferable that themeasuring means determines that the temperatures of the object are onthe increase when the intensities of the first interfered light arehigher than those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on the increase, the temperatures of the object areon the decrease when the intensities of the first interfered light arelower than those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on the increase; and the measuring means judgesthat the temperatures of the object are on the decrease when theintensities of the first interfered light are higher than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on thedecrease, the temperatures of the object are on the increase when theintensities of the first interfered light are lower than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on thedecrease.

In the above-described measuring device, it is preferable that theirradiating means includes a semiconductor laser having a characteristicthat the first wavelength of the first laser beams is longer than thesecond wavelength of the second laser beams, and the measuring devicemeasures a physical quantity, a temperature, or a direction of changesof a temperature of the object to be measured.

In the above-described measuring device, it is preferable that themeasuring means determines that the temperatures of the object are onthe decrease when the intensities of the first interfered light arehigher than those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on the increase, the temperatures of the objectsare on the increase when the intensities of the first interfered lightare lower than those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on the increase; and the measuring means determinesthat the temperatures of the object are on the increase when theintensities of the first interfered light are higher than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on thedecrease, the temperatures of the objects are on the decrease when theintensities of the first interfered light are lower than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on thedecrease.

In the above-described measuring device, it is preferable that theirradiating means is so arranged that when the second wavelength of theis second interfered light is represented by λ, a thickness of theobject to be measured is represented by d, and a refractive index of theobject to be measured is represented by n, a difference Δλ between thefirst wavelength of the first interfered light and the second wavelengthof the second interfered light satisfies

|Δλ|<λ²/(2nd+λ).

The above-described object of the present invention is achieved by ameasuring device for irradiating a laser beam of coherence to an objectto be measured to measure changing amounts of temperatures of the objectto be measured, based on intensities of reflected light or interferedlight on or by the object, the device comprising: irradiating meansincluding angle changing means which changes an incident angle of thelight of coherence to be irradiated to the object for irradiating thelight of coherence to the object; and measuring means which, before atemperature measuring operation, changes an incident angle of the lightof coherence on the object to predict a maximum value and a minimumvalue of the intensities of the interfered light, and, in thetemperature measuring operation, measures temperatures of the object,based on measured intensities of the interfered light and the predictedmaximum and minimum value.

In the above-described measuring device, it is preferable that the anglechanging means changes the incident angle so that the maximum and theminimum values of the intensities of the interfered light are given atleast in one set.

In the above-described measuring device, it is preferable that when awavelength of the light of coherence to be irradiated is represented byλ, an incident angle is represented by θ, a thickness of the object tobe measured is represented by d, and a refractive index thereof isrepresented by n, an angle change Δθ of the incident angle in thepredicting step satisfies a formula

Δθ≧sin⁻¹ [n ²−{(n²−sin²θ)^(½)−λ/4d} ²]^(½)−θ.

In the above-described measuring device, it is preferable that the anglechanging means changes a location of a light source which emits thelight of coherence to change the incident angle of the light ofcoherence with respect to the object to be measured.

In the above-described measuring device, it is preferable that the anglechanging means includes a mirror disposed in an optical path between alight source for generating the light coherence and the object to bemeasured for reflecting the light irradiated on the object to bemeasured; and a lens which refracts light reflected from the mirror,themirror being rotated to change an the incident angle of the light ofcoherence on the object.

In the above-described measuring device, it is preferable that theirradiating means changes intensities of the laser beams to beirradiated to the object to be measured, based on temperatures of theobject to be measured.

In the above-described measuring device, it is preferable that theirradiating means maintains or increases intensities of the laser beamsto be irradiated to the object to be measured when the temperature ofthe object is rising, and maintains or decreases intensities of thelaser beams when the temperature is falling.

In the above-described measuring device, it is preferable that themeasuring device includes means for decreasing the intensities of thelaser beams to be irradiated to the object to be measured, and theintensities of the laser beams to be irradiated to the object to bemeasured are decreased based on the temperature of the object to bemeasured.

In the above-described measuring device, it is preferable that themeasuring device further comprises a container for the object to beplaced in, the container having optical windows on which light to beirradiated to the object to be measured and which exit reflected lightor transmitted light of the irradiated light on or by surfaces thereof,and at least one surface of the optical windows being slanted withrespect to the optical axis of the laser beams so that no interferenceof reflected light inside each of the optical windows and between theoptical windows takes place.

The above-described object of the present invention is achieved by ameasuring device comprising: a first measuring device which measures aphysical quantity at a first measured point of an object to be measuredbeing carried; a second measuring device which is disposed at a mountposition for the object to be mounted on and measures a physicalquantity at a second measured point near said first measured point whenthe object is mounted on said mount position; and setting and correctingmeans which set a measured result given by the first measuring device asan initial measurement of the second measuring device, or which correcta measurement of the second measuring device based on a measured resultgiven by the first measuring device.

The above-described object of the present invention is achieved by ameasuring device comprising: a first measuring device which measures aphysical quantity at a first measured point of an object to be measuredbeing carried; a second measuring device which is disposed at a mountposition for the object to be mounted on and measures a physicalquantity at a second measured point near said first measured point whenthe object is mounted on said mount position; and setting and correctingmeans which set a measured result given by the second measuring deviceas an initial measurement of the first measuring device, or whichcorrects a measurement of the first measuring device based on a measuredresult given by the second measuring device.

In the above-described measuring device, it is preferable that a laserbeam source which is commonly used for the first measuring device andthe second measuring device, and splitter means which split laser beamsemitted by the laser beam source; the first measuring device is arrangedso as to be incident to one of the laser beams split by the splittermeans; and the second measuring device is arranged so as to be incidentto another of laser beams split by the splitter means.

In the above-described measuring device, it is preferable that thephysical quantity is a temperature.

The above-described object of the present invention is achieved by ameasuring method using the above-described measuring device, the firstmeasuring device measures temperatures at the first measured point whenthe object to be measured is carried; the second measuring devicemeasures temperatures at the second measured point when the object to bemeasured is mounted at said mount position; the setting and correctingmeans correct a measured result provided by the second measuring deviceto agree with a measured result given by the first measuring device whenthe object being carried is stopped at the mount position; and thesetting and correcting means correct a result given by the firstmeasuring device to agree with a measured result given by the secondmeasuring device when the object is started to be carried from the mountposition.

The above-described object of the present invention is achieved by amethod for fabricating a semiconductor device, in which requiredtreatments are conducted on a semiconductor substrate while a physicalquantity of the semiconductor substrate is measured by a measuringmethod, the measuring method irradiating laser beams to thesemiconductor substrate to measure a physical quantity of thesemiconductor substrate, pulsed laser beams are irradiated as to thesemiconductor substrate, first laser beams of a first wavelength of thepulsed laser beams and second laser beams of a second wavelength thereofare used to measure the physical quantity of the semiconductorsubstrate, the first wavelength being oscillated after rises of thepulsed laser beams, the second wavelength being oscillated thereafter.

In the above-described fabricating method, it is preferable that therequired treatments is at least one of heat treatments, ionimplantation, etching, diffusion, pretreatments and deposition.

The above-described object of the present invention is achieved by amethod for measuring a wavelength comprising passing light to bemeasured having coherence through a reference substance having apre-known refractive index and a pre-known thickness to apply the lightto be measured in parallel rays, and measuring a wavelength change ofthe light to be measured, based on an intensity change of transmittedlight or reflected light of the light to be measured.

In the above-described method, it is preferable that the light to bemeasured is pulsed laser beams.

In the above-described method, it is preferable that interferingconditions of the light are changed before a wavelength measuringoperation to detect in advance a direction of the wavelength changeaccording to the intensity change of the transmitted light or reflectedlight.

In the above-described method, it is preferable that a refractive indexof the reference substance or a thickness thereof is changed to changethe interfering conditions of the light.

In the above-described method, it is preferable that a temperature ofthe reference substance is changed to change the refractive index or thethickness.

In the above-described method, it is preferable that an incident angleof the light to be measured with respect to the reference substance ischanged to change the interfering conditions of the light.

In the above-described method, it is preferable that an intensity of thetransmitted light or the reflected light of the light to be measured atthe start of a wavelength measuring operation is a set value between amaximum value of its changed intensities and minimum value thereof.

In the above-described method, it is preferable that the light to bemeasured is applied to the reference substance via optical windows, atleast one surface of the optical windows is slanted with respect to theoptical axis of the light to be measured so that no interference iscaused by reflected light of the light to be measured on said onesurface.

The above-described object of the present invention is achieved by adevice for measuring a wavelength comprising: a reference substancehaving a pre-known refractive index; irradiating means for applying tothe reference substance the light to be measured in parallel rays whichpass the reference substance and has coherence; and measuring means formeasuring a wavelength change of the light to be measured, based on anintensity change of transmitted light of the light to be measured orreflected light thereof.

In the above-described device, it is preferable that the light to bemeasured is pulsed laser beams.

In the above-described device, it is preferable that interferingconditions of the light are changed before a wavelength measuringoperation to detect in advance a direction of the wavelength changeaccording to the intensity change of the transmitted light or reflectedlight.

In the above-described device, it is preferable that a refractive indexof the reference substance or a thickness thereof is changed to changethe interfering conditions of the light.

In the above-described device, it is preferable that a temperature ofthe reference substance is changed to change the refractive index or thethickness.

In the above-described device, it is preferable that an incident angleof the light to be measured with respect to the reference substance ischanged to change the interfering conditions of the light.

In the above-described device, it is preferable that an intensity of thetransmitted light or the reflected light of the light to be measured atthe start of a wavelength measuring operation is a set value between amaximum value of its changed intensities and a minimum value thereof.

In the above-described device, it is preferable that the light to bemeasured is applied to the reference substance via optical windows, atleast one surface of the optical windows is slanted with respect to theoptical axis of the light to be measured so that no interference iscaused by reflected light of the light to be measured on said onesurface.

According to the present invention, pulsed laser beams are irradiatedonto the object to be measured, first laser beams of a first wavelengthof the pulsed laser beams and second laser beams of a second wavelengththereof are used to measure the physical quantity of the object, thefirst wavelength being oscillated after rises of the pulsed laser beams,the second wavelength being oscillated thereafter, whereby physicalquantities and the direction of change thereof can be preciselymeasured.

In the above-described measuring method, temperatures of the object aremeasured, based on changes of intensities of first interfered light ofreflected light or transmitted light of one of the first laser beams onor by the object, and changes of intensities of second interfered lightof reflected light or transmitted light of one of the second laser beamson or by the object, whereby temperature of the object to be measuredand the direction of change thereof can be precisely measured.

In the above-described measuring method, the temperatures of the objectare determined to be on the increase or decrease, based on a directionof the changes of intensities of the first or the second interferedlight and on a difference between the intensity of the first interferedlight and that of the second interfered light, whereby temperature ofthe object to be measured and the direction of change thereof can beprecisely measured.

In the above-described measuring method, the measuring method measuresthe physical quantity, temperatures, or a direction of changes oftemperatures of the object to be measured, by using a semiconductorlaser having a characteristic that the first wavelength of the firstlaser beams is shorter than the second wavelength of the second laserbeams, whereby temperature of the object can be precisely measured.

In the above-described measuring method, the temperatures of the objectare determined to be on the increase when the intensities of the firstinterfered light are higher than those of the second interfered light atthe time that the intensities of the first interfered light or those ofthe second interfered light are on the increase, the temperatures of theobjects are determined to be on the decrease when the intensities of thefirst interfered light are lower than those of the second interferedlight at the time that the intensities of the first interfered light orthose of the second interfered light are on the increase, thetemperatures of the object are determined to be on the decrease when theintensities of the first interfered light are higher than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on thedecrease, the temperatures of the objects are determined to be on theincrease when the intensities of the first interfered light are lowerthan those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on the decrease, whereby temperature of the objectto be measured and the direction of change thereof can be reliablymeasured.

In the above-described measuring method, the measuring method measuresthe physical quantity, temperatures, or a direction of changes oftemperatures of the object to be measured by using a semiconductor laserhaving a characteristic that the first wavelength of the first laserbeams is longer than the second wavelength of the second laser beams,whereby temperature of the object can be precisely measured.

In the above-described measuring method, the temperatures of the objectare determined to be on the decrease when the intensities of the firstinterfered light are higher than those of the second interfered light atthe time that the intensities of the first interfered light or those ofthe second interfered light are on the increase, the temperatures of theobjects are determined to be on the increase when the intensities of thefirst interfered light are lower than those of the second interferedlight at the time that the intensities of the first interfered light orthose of the second interfered light are on the increase, thetemperatures of the object are determined to be on the increase when theintensities of the first interfered light are higher than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on thedecrease, the temperatures of the objects are determined to be on thedecrease when the intensities of the first interfered light are lowerthan those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on the decrease, whereby temperature of the objectto be measured and the direction of change thereof can be reliablymeasured.

In the above-described measuring method, when the second wavelength ofthe second interfered light is represented by λ, a thickness of theobject to be measured is represented by d, and a refractive index of theobject to be measured is represented by n, a difference Δλ between thefirst wavelength of the first interfered light and the second wavelengthof the second interfered light satisfies

|Δλ|<λ²/(2nd+λ),

whereby interference suitable for determining the direction of change ofthe temperature can be obtained.

According to the present invention, the method comprises: a predictingstep of, before a temperature measuring operation, predicting a maximumvalue and a minimum value of the intensities of the interfered light;and a measuring step of measuring the change amounts of the temperaturesof the object, based on the intensities of the interfered light, and thepredicted maximum and minimum values, whereby the temperaturemeasurement can be started immediately after the start of measuring theintensities of interfered light.

In the above-described measuring method, the incident angle in thepredicting step is so changed that the maximum and the minimum values ofthe intensities of the interfered light are given at least in one set,whereby the maximum and the minimum values of the intensities of theinterfered light can be predicted within the shortest time.

In the above-described measuring method, when a wavelength of the lightof coherence to be irradiated is represented by λ, an incident angle isrepresented by θ, a thickness of the object to be measured isrepresented by d, and a refractive index thereof is represented by n, anangle change Δθ of the incident angle in the predicting step satisfies aformula

Δθ≧sin⁻¹ [n ²−{(n ²−sin²θ)^(½)−λ/4d} ²]^(½)−θ,

whereby the maximum and the minimum values of the intensities of theinterfered light can be reliably predicted.

In the above-described measuring method, oscillating intensities of thelaser beams to be irradiated to the object to be measured are changedbased on temperatures of the object to be measured, whereby the methodcan measure a wide range of temperatures.

In the above-described measuring method, intensities of the laser beamsto be irradiated to the object to be measured are constant or increasedwhen the temperature of the object is rising, and intensities of thelaser beams are constant or decreased when the temperature is falling,whereby the method can measure a wide range of temperatures.

In the above-described measuring method, the intensities of the laserbeams to be irradiated to the object to be measured are decreased basedon the temperature of the object to be measured, whereby the temperatureof the object can be precisely measured by using the stable laser beams.

In the above-described measuring method, one or plural optical windowsare provided in a measuring light path, at least one surface of theoptical windows is slanted with respect to the optical axis of the laserbeams, whereby no interference of reflected light inside each of theoptical windows and between the optical windows takes place.

According to the present invention, the measuring device comprises:irradiating means which oscillates pulsed laser beams to irradiate firstlaser beams of a first wavelength which is oscillated after rises of thepulsed laser beams, and second laser beams which is oscillatedthereafter and differs from the first wavelength; and measuring meanswhich measures the physical quantity of the object to be measured by theuse of the first laser beams and the second laser beams irradiated bythe irradiating means, whereby the direction of change of the physicalquantities can be precisely measured with a simple structure.

In the above-described measuring device, the measuring means measurestemperatures of the object to be measured, based on changes ofintensities of first interfered light of reflected light or transmittedlight of one of the first laser beams on or by the object, or changes ofintensities of second interfered light of reflected light or transmittedlight of one of the second laser beams on or by the object, whereby thetemperature and the direction of change thereof can be preciselymeasured with a simple structure.

In the above-described measuring device, the measuring means determinesthat the temperatures of the object are on the increase or decrease,based on a direction of the changes of intensities of the first or thesecond interfered light and on a difference between the intensity of thefirst interfered light and that of the second interfered light, wherebythe temperature and the direction of change thereof can be preciselymeasured with a simple structure.

In the above-described measuring device, the irradiating means includesa semiconductor laser having a characteristic that the first wavelengthof the first laser beams is shorter than the second wavelength of thesecond laser beams, and the measuring device measures the physicalquantity, a temperature, or a direction of changes of a temperature ofthe object to be measured, whereby they can be precisely measured.

In the above-described measuring device, the measuring means determinesthat the temperatures of the object are on increase when the intensitiesof the first interfered light are higher than those of the secondinterfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on theincrease, the temperatures of the object are on the decrease when theintensities of the first interfered light are lower than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on theincrease; and the measuring means determines that the temperatures ofthe object are on the decrease when the intensities of the firstinterfered light are higher than those of the second interfered light atthe time that the intensities of the first interfered light or those ofthe second interfered light are on the decrease, the temperatures of theobject are on the increase when the intensities of the first interferedlight are lower than those of the second interfered light at the timethat the intensities of the first interfered light or those of thesecond interfered light are on the decrease, whereby the temperature andthe direction of change thereof can be precisely measured with a simplestructure.

In the above-described measuring device, the irradiating means includesa semiconductor laser having a characteristic that the first wavelengthof the first laser beams is longer than the second wavelength of thesecond laser beams, and the measuring device measures a physicalquantity, a temperature, or a direction of changes of a temperature ofthe object to be measured, whereby the device can measure a wide rangeof them.

In the above-described measuring device, the measuring means judges thatthe temperatures of the object are on decrease when the intensities ofthe first interfered light are higher than those of the secondinterfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on theincrease, the temperatures of the objects are on the increase when theintensities of the first interfered light are lower than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are on theincrease; and the measuring means determines that the temperatures ofthe object are on the increase when the intensities of the firstinterfered light are higher than those of the second interfered light atthe time that the intensities of the first interfered light or those ofthe second interfered light are on the decrease, the temperatures of theobjects are on the decrease when the intensities of the first interferedlight are lower than those of the second interfered light at the timethat the intensities of the first interfered light or those of thesecond interfered light are on the decrease, whereby the temperature andthe direction of change thereof can be precisely measured with a simplestructure.

In the above-described measuring device, the irradiating means is soarranged that when the second wavelength of the second interfered lightis represented by λ, a thickness of the object to be measured isrepresented by d, and a refractive index of the object to be measured isrepresented by n, a difference Δλ between the first wavelength of thefirst interfered light and the second wavelength of the secondinterfered light satisfies

|Δλ|<λ²/(2nd+λ),

whereby interference suitable for determining the direction of change ofthe temperature can be obtained.

According to the present invention, the device comprises: irradiatingmeans including angle changing means which changes an incident angle ofthe light of coherence to be irradiated to the object for irradiatingthe light of coherence to the object; and measuring means which, beforea temperature measuring operation, changes an incident angle of thelight of coherence on the object to predict a maximum value and aminimum value of the intensities of the interfered light, and, in thetemperature measuring operation, measures temperatures of the object,based on measured intensities of the interfered light and the predictedmaximum and minimum value, whereby the temperature measurement can bestarted immediately after the start of measuring the intensities ofinterfered light.

In the above-described measuring device, the angle changing meanschanges the incident angle so that the maximum and the minimum values ofthe intensities of the interfered light are given at least in one set,whereby the maximum and the minimum values of the intensities of theinterfered light can be predicted within the shortest time.

In the above-described measuring device, when a wavelength of the lightof coherence to be irradiated is represented by λ, an incident angle isrepresented by θ, a thickness of the object to be measured isrepresented by d, and a refractive index thereof is represented by n, anangle change Δθ of the incident angle in the predicting step satisfies aformula

Δθ≧sin⁻¹ [n ²−{(n ²−sin²θ)^({fraction (1/12)})−λ4d} ²]^(½)−θ,

whereby the maximum and the minimum values of the intensities of theinterfered light can be reliably predicted.

In the above-described measuring device, the angle changing meanschanges a location of a light source which emits the light of coherenceto change the incident angle of the light of coherence with respect tothe object to be measured, whereby the interfering conditions of thelight can be easily changed so that the maximum and the minimum valuesof the intensities of the interfered light can be predicted.

In the above-described measuring device, the angle changing meansincludes a mirror disposed in an optical path between a light source forgenerating the light coherence and the object to be measured forreflecting the light irradiated on the object to be measured; and a lenswhich refracts light reflected from the mirror,the mirror being rotatedto change an the incident angle of the light of coherence on the object,whereby the interfering conditions of the light can be easily changed sothat the maximum and the minimum values of the intensities of theinterfered light can be predicted.

In the above-described measuring device, the irradiating means changesintensities of the laser beams to be irradiated onto the object to bemeasured, based on temperatures of the object to be measured, wherebythe temperature of the object can be measured up to a highertemperature.

In the above-described measuring device, the irradiating means maintainsor increases intensities of the laser beams to be irradiated to theobject to be measured when the temperature of the object is rising, andmaintains or decreases intensities of the laser beams when thetemperature is falling, whereby the temperature of the object can bemeasured up to a higher temperature.

In the above-described measuring device, the measuring device includesmeans for decreasing the intensities of the laser beams to be irradiatedto the object to be measured, and the intensities of the laser beams tobe irradiated to the object to be measured are decreased based on thetemperature of the object to be measured, whereby the temperature of theobject can be precisely measured by using the stable laser beams.

In the above-described measuring device, the measuring device furthercomprises a container for the object to be placed in, the containerhaving optical windows on which light to be irradiated to the object tobe measured and light which exits reflected light or transmitted lightof the irradiated light on or by surfaces of the object to be measuredthereof, and at least one surface of the optical windows is slanted withrespect to the optical axis of the laser beams, whereby no interferenceof reflected light inside each of the optical windows and between theoptical windows takes place.

According to the present invention, the measuring device comprises: afirst measuring device which measures a physical quantity at a firstmeasured point of an object to be measured is carried; a secondmeasuring device which is disposed at a mount position for the object tobe mounted on and measures a physical quantity at a second measuredpoint near said first measured point when the object is mounted on saidmount position; and setting and correcting means which set a measuredresult given by the first measuring device as an initial measurement ofthe second measuring device, or which corrects a measurement of thesecond measuring device based on a measured result given by the firstmeasuring device, whereby physical quantities of the object can becontinuously measured.

According to the present invention, the measuring device comprises: afirst measuring device which measures a physical quantity at a firstmeasured point of an object to be measured being carried; a secondmeasuring device is disposed at a mount position for the object to bemounted on and measures a physical quantity at a second measured pointnear said first measured point when the object is mounted on said mountposition; and setting and correcting means which set a measured resultgiven by the second measuring device as an initial measurement of thefirst measuring device, or which corrects a measurement of the firstmeasuring device based on a measured result given by the secondmeasuring device, whereby physical quantities of the object can becontinuously measured.

In the above-described measuring device, a laser beam source which iscommonly used for the first measuring device and the second measuringdevice, and splitter means which split laser beams emitted by the laserbeam source; the first measuring device is arranged to be incident toone of laser beams split by the splitter means; and the second measuringdevice is arranged to be incident to another of the laser beams split bythe splitter means, whereby physical quantities of the object can becontinuously measured with a simple structure.

According to the present invention, the measuring method uses theabove-described measuring device, the first measuring device measurestemperatures at the first measured point when the object to be measuredis carried; the second measuring device measures temperatures at thesecond measured point when the object to be measured is mounted at saidmount position; the setting and correcting means correcting a measuredresult given by the second measuring device to agree with a measuredresult given by the first measuring device when the object being carriedis stopped at the mount position; and the setting and correcting meanscorrects a result provided by the first measuring device to agree with ameasured result provided by the second measuring device when the objectstart to be carried from the mount position, whereby physical quantitiesof the object can be continuously measured.

According to the present invention, in the method for fabricating asemiconductor device, required treatments are conducted on asemiconductor substrate while a physical quantity of the semiconductorsubstrate is measured by a measuring method, the measuring methodirradiates laser beams onto the semiconductor substrate to measure aphysical quantity of the semiconductor substrate, pulsed laser beams areirradiated onto the semiconductor substrate, first laser beams of afirst wavelength of the pulsed laser beams and second laser beams of asecond wavelength thereof are used to measure the physical quantity ofthe semiconductor substrate. The first wavelength are oscillated afterrises of the pulsed laser beams. The second wavelength are oscillatedthereafter, whereby physical quantities of the semiconductor substratecan be continuously measured. The required treatments may be heattreatments, ion implantation, etching, diffusion, pretreatments ordeposition.

According to the present invention, the wavelength measuring methodcomprises the steps of passing light to be measured having coherencethrough a reference substance having a predetermined refractive indexand a predetermined thickness to apply the light to be measured inparallel rays, and measuring a wavelength change of the light to bemeasured, based on an intensity change of transmitted light or reflectedlight of the light to be measured, whereby quickly shifting wavelengthscan be measured without allocating a scanning time for spectraldiffraction.

In the above-described method, the light to be measured may be laserbeams or pulsed laser beams.

In the above-described method, interfering conditions of the light arechanged before a wavelength measuring operation to detect in advance adirection of the wavelength change according to the intensity change ofthe transmitted light or reflected light, whereby the direction ofchange of the wavelength can be measured.

In the above-described method, a refractive index of the referencesubstance or a thickness thereof is changed, whereby the interferingcondition of the light can be easily changed.

In the above-described method, a temperature of the reference substanceis changed, whereby the interfering condition of the light can be easilychanged.

In the above-described method, an incident angle of the light to bemeasured with respect to the reference substance is changed, whereby theinterfering condition of the light can be easily changed.

In the above-described method, an intensity of the transmitted light orthe reflected light of the light to be measured at the start of awavelength measuring operation is a set value between a maximum value ofits changed intensities and minimum value thereof, whereby change of thewavelength can be precisely measured.

In the above-described method, the light to be measured is applied tothe reference substance via optical windows, at least one surface of theoptical windows is slanted with respect to the optical axis of the lightto be measured, whereby no interference is caused by reflected light ofthe light to be measured on said one surface.

According to the present invention, the wavelength measuring devicecomprises: a reference substance having a pre-known refractive index;irradiating means for applying to the reference substance the light tobe measured in parallel rays which pass the reference substance and hascoherence; and measuring means for measuring a wavelength change of thelight to be measured, based on an intensity change of transmitted lightof the light to be measured or reflected light thereof, whereby quicklyshifting wavelengths can be measured without allocating a scanning timefor spectral diffraction. In addition, the wavelength measuring devicecan be small in size.

In the above-described device, the light to be measured may be laserbeams or pulsed laser beams.

In the above-described device, interfering conditions of the light arechanged before a wavelength measuring operation to detect in advance adirection of the wavelength change according to the intensity change ofthe transmitted light or reflected light, whereby the direction ofchange of the wavelength can be measured.

In the above-described device, a refractive index of the referencesubstance or a thickness thereof is changed, whereby the interferingconditions of the light can be easily changed.

In the above-described device, a temperature of the reference substanceis changed to change the refractive index or the thickness, whereby theinterfering conditions of the light can be easily changed.

In the above-described device, an incident angle of the light to bemeasured with respect to the reference substance is changed, whereby theinterfering conditions of the light can be easily changed.

In the above-described device, an intensity of the transmitted light orthe reflected light of the light to be measured at the start of awavelength measuring operation is a set value between a maximum value ofits changed intensities and a minimum value thereof, whereby the changeof the wavelength can be precisely measured.

In the above-described device, the light to be measured is applied tothe reference substance via optical windows, at least one surface of theoptical is windows is slanted with respect to the optical axis of thelight to be measured, whereby no interference is caused by reflectedlight of the light to be measured on said one surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the device for measuring temperaturesaccording to a first embodiment of the present invention.

FIG. 2 is a view of waveforms of pulsed laser beams irradiated to asubstrate to be measured showing transient changes of interfered lightintensities.

FIG. 3 is a graph of relationships between measured temperatures andinterfered light intensities of the device for measuring temperaturesaccording to the first embodiment of the present invention.

FIGS. 4A to C are graphs of wavelength changes and interfered lightintensity changes of pulsed laser beams of the device for measuringtemperatures according to the first embodiment of the present invention.

FIGS. 5A to C are views explaining the measuring principle of the devicefor measuring temperatures according to the first embodiment of thepresent invention.

FIG. 6 is a flow chart of an algorithm of the device for measuringtemperatures according to the first embodiment of the present invention.

FIG. 7 is a graph of measured results of the device for measuringtemperatures of the first embodiment of the present invention.

FIG. 8 is a graph of relationships between measured temperatures andinterfered light intensities of the device for measuring temperaturesaccording to a second embodiment of the present invention.

FIGS. 9A to C are graphs of wavelength changes and interfered lightintensity changes of pulsed laser beams of the device for measuringtemperatures according to the second embodiment of the presentinvention.

FIGS. 10A to C are views explaining a measuring principle of the devicefor measuring temperatures according to the second embodiment of thepresent invention.

FIG. 11 is a flow chart of an algorithm of the device for measuringtemperatures according to the second embodiment of the presentinvention.

FIG. 12 is a block diagram of the device for measuring temperaturesaccording to a third embodiment of the present invention.

FIG. 13 is a block diagram of an experimental device for measuringlimits of pulsed laser beams according to the present invention.

FIGS. 14A to C are graphs of measured results of the experimental deviceof FIG. 13.

FIG. 15 is a block diagram of the device for measuring temperaturesaccording to a fourth embodiment of the present invention.

FIGS. 16A and B are graphs of relationships between interfered lightintensities and time of the device for measuring temperatures accordingto a fifth embodiment of the present invention.

FIG. 17 is a block diagram of the device for measuring temperaturesaccording to a fifth embodiment of the present invention.

FIG. 18 is a block diagram of the device for measuring temperaturesaccording to a sixth embodiment of the present invention.

FIG. 19 is a block diagram of the device for measuring temperaturesaccording to a seventh embodiment of the present invention.

FIG. 20 is a block diagram of the device for measuring temperaturesaccording to an eighth embodiment of the present invention.

FIG. 21 is a view explaining a measuring principle of the device formeasuring temperatures according to the eighth embodiment of the presentinvention.

FIG. 22 is a graph of relationships between interfered light intensitiesand incident angles of the device for measuring temperatures accordingto the eighth embodiment of the present invention.

FIG. 23 is a graph of interfered light intensities and measuredtemperatures of the device for measuring temperatures according to theeighth embodiment of the present invention.

FIG. 24 is a block diagram of the device for measuring temperaturesaccording to the eighth embodiment of the present invention.

FIGS. 25A and B are diagrams of a first variation of the device formeasuring temperatures according to the eighth embodiment of the presentinvention.

FIGS. 26A and B are diagrams of a second variation of the device formeasuring temperatures according to the eighth embodiment of the presentinvention.

FIGS. 27A and B are diagrams of a third variation of the device formeasuring temperatures according to the eighth embodiment of the presentinvention.

FIG. 28 is a block diagram of the device for measuring temperaturesaccording to a ninth embodiment of the present invention.

FIG. 29 is a graph of measured results of the device for measuringtemperatures according to the ninth embodiment of the present invention.

FIG. 30 is a graph of measured results of the conventional device formeasuring temperatures.

FIG. 31 is a block diagram of a variation of the device for measuringtemperatures according to the ninth embodiment of the present invention.

FIG. 32 is a block diagram of the device for measuring temperaturesaccording to a tenth embodiment of the present invention.

FIG. 33 is a graph of measured results of the device for measuringtemperatures according to the tenth embodiment of the present invention.

FIG. 34 is a graph of measured results of the conventional device formeasuring temperatures.

FIG. 35 is a block diagram of a first variation of the device formeasuring temperatures according to the tenth embodiment of the presentinvention.

FIG. 36 is a block diagram of a second variation of the device formeasuring temperatures according to the tenth embodiment of the presentinvention.

FIG. 37 is a block diagram of a third variation of the device formeasuring temperatures according to the tenth embodiment of the presentinvention.

FIG. 38 is a block diagram of a fourth variation of the device formeasuring temperatures according to the tenth embodiment of the presentinvention.

FIGS. 39A and B are diagrams of the device for measuring temperaturesaccording to an eleventh embodiment of the present invention.

FIGS. 40A to D are views explaining a method for measuring temperaturesby the device for measuring temperatures according to the eleventhembodiment of the present invention.

FIGS. 41A to D are views explaining the device for measuringtemperatures by the device for measuring temperatures according to theeleventh embodiment of the present invention.

FIG. 42 is a block diagram of a cluster device the device for measuringtemperatures according to the eleventh embodiment of the presentinvention is applied to.

FIG. 43 is a block diagram of the wavelength measuring device accordingto a twelfth embodiment of the present invention.

FIGS. 44A and B are views of examples of the reference substance used inthe wavelength measuring device according to the twelfth embodiment ofthe present invention.

FIG. 45 is a view explaining the measuring principle of the wavelengthmeasuring device according to the twelfth embodiment of the presentinvention.

FIG. 46 is a graph of measurement results of the wavelength measuringdevice according to the twelfth embodiment of the present invention.

FIG. 47 is a block diagram of the wavelength measuring device accordingto a thirteenth embodiment of the present invention.

FIG. 48 is a block diagram of the wavelength measuring device accordingto a fourteenth embodiment of the present invention.

FIG. 49 is a block diagram of the wavelength measuring device accordingto a fifteenth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

The device for measuring a temperature according to a first embodimentof the present invention will be explained with reference to FIGS. 1 to5.

FIG. 1 is a block diagram of the device for measuring a temperatureaccording to the first embodiment.

In the device for measuring a temperature according to the presentembodiment, coherent laser beams are applied to a measurable part of anobject to be measured, e.g., a semiconductor substrate 6. Thesemiconductor substrate 6 has opposed surfaces which are polished toreflect the applied coherent laser beams, and variations in the observedmutually interfering intensities of the reflected light from thepolished surfaces so as to give the temperature of the object.

The semiconductor substrate 6 whose temperature is desired to bemeasured is placed in a chamber 4 on a heater 5 for heating thesemiconductor substrate 6.

The semiconductor substrate 6 whose temperature to be measured is anapproximately 0.5 mm-thick silicon substrate. The semiconductorsubstrate 6 may be another semiconductor substrate, such as a GaAssubstrate, an InP substrate or others, in addition to being a siliconsubstrate.

The semiconductor laser 1 is connected to a pulse power source 11. Thepulse power source 11 supplies pulsed current of, e.g., 50 Hz, so thatthe semiconductor laser 1 emits pulsed laser beams modulated with thisfrequency. A suitable semiconductor laser is a NDL5600 by NEC (anInGaAsP phase shift-type DFT-DC-PBH laser diode for use in 1310nm-optical fiber communication; output: approximately 0.5 mW).Preferably, the semiconductor laser 1 is a semiconductor laser with anAPC which can emit pulses at a pulse frequency above 10 Hz.

The chamber 4 has optical windows (not shown) through which pulsed laserbeams are applied onto and reflected from the semiconductor substrate 6in the chamber 4. The chamber 4 itself may be made of transparentmaterial without the optical windows.

Pulsed laser beams emitted by the semiconductor laser 1 are led to acollimating optical unit 3 through an optical fiber 2. The pulsed laserbeams are made into parallel ray bundles by the collimating optical unit3 to be applied to the semiconductor substrate 6 in the chamber 4.

An interfered light reflected from the semiconductor substrate 6 isdetected by a photo detector 7. A suitable photo detector is a B4246 byHamamatsu Photonics (a Ge photovoltaic device).

Received signals derived from the light detected by the photo detector7, which are analog signals, are supplied to an A/D converting unit 9through a data signal line 8. The A/D converting unit 9 converts thedetected signals to digital signals and outputs them to a computer 10.Based on these digital detected signals, the computer 10 calculatesintensity variations due to mutual interference in the reflected lightand, based on computation results, gives temperature changes, thedirection of the change, and an accurate measured temperature.

The present embodiment uses the fact that when a pulsed laser beam isemitted by the semiconductor laser 1, the laser beam initially has ashorter wavelength (a first wavelength p1) by some Angstroms, when itrises, and thereafter has a longer wavelength (a second wavelength p2).As evidence of this fact, FIG. 2 shows an observed waveform ofintensities of interfered light produced when a pulsed laser beam isapplied to the semiconductor substrate 6 whose temperature is rising.FIG. 2 shows the case where pulsed laser beams with a 10 msec-pulsewidth are applied to the substrate 6. Voltages are taken on the verticalaxis, and one division corresponds to 2 V. Time is taken on thehorizontal axis, and one division corresponds to 1 ms.

As shown in FIG. 2, immediately after a laser beam pulse rises, theinterfered light intensity is highest and thereafter gradually decreasesto a stable, approximately constant value after approximately 2 msec.This transient changes do not occur in the case where a pulsed laserbeam is generated by choppering a continuous laser beam. The temperatureof the substrate 6 is constant while measuring in FIG. 2.

In the case where the temperature of the substrate 6 is constant, theintensity of interfered light depends on the wavelength of the sourcelaser beam. Thus it is found in the graph of FIG. 2 that the wavelengthof the pulsed laser beam changes transiently. In this embodiment, thepulsed laser beam has a short wavelength immediately after rising.

In the present embodiment, laser beams with an approximately 10msec-pulse width are used. The laser beams may be sampled at theirinitial wavelength p1, 0.12 msec after the pulse begins to rise, andagain at their second wavelength p2, 8 msec after the pulse rises. It ispreferred that the laser beams of the first wavelength p1 begin tooscillate within approximately 0.5 msec after the pulse begins to rise.

In the present invention, the pulses may equally well be sampled 0.12msec after the rise of any one pulse, and again 8 msec after the rise ofany other pulse.

Next, the measuring principles of the device for measuring a temperatureaccording to the present embodiment will be explained with reference toFIGS. 3 to 5.

FIG. 3 is a graph of the relationships between the measured temperature(T) and the interfered light intensities (11, 12). FIGS. 4A to C aregraphs showing wavelength changes of pulsed laser beams and interferedlight intensity changes. FIG. 5A is a graph showing the intensities ofinterfered light of the first and second wavelengths p1, p2. FIG. 5B isa graph showing transient temperature changes of the semiconductorsubstrate 6. FIG. 5C is a table showing the relationship between theinterfered light and temperature changes in semiconductor substrate 6.

In the device for measuring a temperature according to the presentembodiment, a silicon substrate, for example, as the semiconductorsubstrate 6, is mounted on the heater 5. When a laser beam emitted bythe semiconductor laser 1 is applied to the semiconductor substrate 6,as shown in FIG. 1, portions of the laser beam reflected from the topand bottom surfaces of the semiconductor substrate 6 mutually interfere.

While the heater 5 is heating the semiconductor substrate 6, so that thetemperature thereof is rising, the laser beams from the semiconductorlaser 1 are applied to the semiconductor substrate 6 via the collimatingoptical unit 3. An interfered light reflected from the polishedreflecting surfaces of semiconductor substrate 6 is detected by thephoto-detector 7, and the intensity of the interfered light is analyzedby the computer 10.

As a result, the temperature versus the interfered light intensitycharacteristic indicated by the solid line in FIG. 3 is given. As thetemperature of the semiconductor substrate 6 is rising, the intensityvariation of the interfered light can be represented by periodicallyrising and falling into a kind of periodical waves similar to sinewaves, i.e. sine-like waves.

This principle is as follows.

Because the dielectric constant (refractive index) of the semiconductorsubstrate 6 and a thickness thereof increase with rising temperaturethereof, the effective optical distance inside the semiconductorsubstrate 6 changes. The phase of that portion of the laser beam whichhas traversed through the semiconductor substrate 6 and which has beenreflected from the bottom surface prior to exiting from the top surfaceshifts according to the temperature change. Thus the resultant phaserelationship between the reflected lights from the top surface and thebottom surface changes.

Accordingly an intensity of interfered light of reflected light on thesemiconductor substrate 6 is changed in a sine-like wave by temperaturechanges. A temperature change ΔT(T) [° C.] for one period is calculatedby the following formula when a thickness of the semiconductor substrate6 is represented by L, and a refractive index thereof is represented byn

ΔT=λ/{2nL(α+β)}

where α=(1/L)×(dL/dT)

β=(1/n)×(dn/dT).

It is difficult to give α and β here. (α+β) is experimentally given.

That is, a temperature change ΔT(T) for one period is given by thefollowing formula, based on a frequency f of an intensity of theinterfered light calculated based on a difference from an experimentalinitial value and a corrected curve of measured temperatures iscalculated by the following fifth order approximation expression.

ΔT(f)=12.278+11.012×f−0.13222×f ²+0.0018399×f ³−1.5803×10⁻⁵ ×f⁴+5.5364×10⁻⁸ ×f ⁵

Thus, a temperature of the semiconductor substrate 6 is decided by atemperature To [° C.] at the start of heating and a number of periods oftemperature changes.

On the other hand, the semiconductor substrate 6 is heated or cooled bythe heater 5, and its temperature rises or lowers. To determine atemperature of the semiconductor substrate 6 it is necessary to know adirection of temperature changes. The principle for this determinationwill be explained.

Pulsed current of approximately 50 Hz is injected into the semiconductorlaser 1 from the pulse power source 11 to apply pulsed laser beams of 50Hz from the semiconductor laser 1 to the semiconductor substrate 6. Thewavelength of the pulsed laser beams emitted from the semiconductorlaser 1 has a characteristic, as shown in FIG. 4A, that the wavelengthis short when it rises and becomes longer when the wavelength reachesits normal state.

The first wavelength p1 (=λ−Δλ) of a pulsed laser beam from thesemiconductor laser 1 at the time of rise is shorter by Δλ than thesecond wavelength p2 (=λ) at its following normal state. Thetemperature-interfered light intensity characteristic showingrelationships between intensities of reflected light of a laser beam ofthe first wavelength p1 (=λ−Δλ) on the semiconductor substrate 6, andtemperatures has, as shown in FIG. 3, the phase advanced by Φ withrespect to that of the laser beam of the second wavelength p2 (=λ).

Suitable interference can be obtained by a maximum difference λΔ betweenthe first wavelength p1 of a pulsed laser beam oscillated within 0.5 msafter rise of the pulsed laser beam, and the second wavelength p2 (=λ)thereof satisfying the relationship of |αλ|<λ²/(2nd+λ) with respect to arefractive index n of the semiconductor substrate 6 and a thickness dthereof.

Based on the above, it is seen that while a temperature of thesemiconductor substrate 6 is increasing, with the interfered lightintensity being increased, an interfered light intensity I2 of thesecond wavelength p2 is lower than an interfered light intensity I1 ofthe first shorter wavelength p1, and with an interfered light intensitybeing decreased, oppositely an interfered light intensity I2 of thesecond wavelength p2 is higher than that I1 of the shorter firstwavelength p1.

It is also seen that while a temperature of the semiconductor substrate6 is decreasing, with the interfered light intensity being increased, aninterfered light intensity I2 of the second wavelength p2 is higher thanan interfered light intensity I1 of the first shorter wavelength p1, andwith an interfered light intensity being decreased, oppositely ainterfered light intensity I2 of the second wavelength p2 is lower thanthat I1 of the shorter first wavelength p1.

With respect to reflected light of a pulsed laser beam shown in FIG. 4A,there are two cases that, as shown in FIG. 4B, the interfered lightintensity is low when the pulsed laser beam rises, and, as shown in FIG.4C, the interfered light intensity is high when the pulsed laser beamrises.

FIG. 4B corresponds to the temperatures T1 with respect to theinterfered light intensity changes of FIG. 3. FIG. 4C corresponds to thetemperatures T2 with respect to the interfered light intensity changesof FIG. 3. FIG. 3 corresponds to the circles and the crosses in FIGS. 4Band C.

Accordingly, it is determined whether a temperature is increasing ordecreasing: by measuring intensities of the interfered light of thereflected light of a pulsed laser beam on the semiconductor substrateimmediately (X) after the rise of the pulsed laser beam, and a certaintime (O) after the rise of the pulsed laser beam to determine whetherthe interfered light intensity at the rise of the pulsed laser beam islow as in FIG. 4B or is high as in FIG. 4C; and by measuring slop of theintensity I1 of interfered light of the first wavelength p1 or theintensity I2 of interfered light of the second wavelength p2 intensityI1.

That is, the following is judged with the vicinity of the crest of thewaveform of the coherent light intensity and the vicinity of the troughthereof out of consideration.

At the time when the intensity I1 of interfered light of the firstwavelength p1 or the intensity I2 of interfered light of the secondwavelength p2 are increasing, it is determined that when an intensity I1of the interfered light of the first wavelength p1 is higher than thatI2 of the interfered light of the second wavelength (I1>I2) atemperature of the semiconductor substrate 6 is rising, and when anintensity I1 of the interfered light of the first wavelength p1 is lowerthan that I2 of the interfered light of the second wavelength (I1<I2), atemperature of the semiconductor substrate 6 is falling. At the timewhen the intensity I1 of interfered light of the first wavelength p1 orthe intensity I2 of interfered light of the second wavelength p2 aredecreasing, it is determined that when an intensity I1 of the interferedlight of the first wavelength p1 is higher than that I2 of theinterfered light of the second wavelength (I1>I2) a temperature of thesemiconductor substrate 6 is falling, and when an intensity I1 of theinterfered light of the first wavelength p1 is higher than that I2 ofthe interfered light of the second wavelength (I1<I2), a temperature ofthe semiconductor substrate 6 is rising.

The method for this determination used in the present embodiment will bespecifically explained. First, pulsed laser beams of a 50 Hz frequencyare applied to the semiconductor substrate 6. Reflected light of theapplied laser beams are received by the photo receptor 7, andintensities of interfered light are stored for the respective pulses. Atthis time, interfered light intensities I1 of the first wavelength p1oscillated within 0.5 msec after the rises of the pulsed laser beams,and interfered light intensities I2 of the second wavelength p2oscillated after 0.5 msec from the rises of the pulsed laser beams asshown in FIGS. 4B and C are extracted and stored, and relationshipsbetween changes of the coherent intensities I1, I2 and time are graphed.

Based on the graph, for example, a temperature of the semiconductorsubstrate 6 is, by the heater 5, increased in a time (t0-tm) and thendecreased in a time (tm-t2), and relationships between intensities ofthe reflected light on the semiconductor substrate 6 and time aremeasured. The measurement result is as shown in FIG. 5A. In FIG. 5A, thesine-like wave in the solid line indicates interfered light intensitiesof the second wavelength p2 (=λ), and the sine-like wave in the brokenline indicates interfered light intensities of the first wavelength p1(=λ−Δλ).

Based on the thus-given interfered light intensities shown in FIG. 5A,temperature changes are given as shown in FIG. B.

The above-described physical relationships are opposite near the crestsand troughs of the intensity waveforms of the interfered light. Becauseintensity differences between interfered light of the first wavelengthp1 and that of the second wavelength p2 are small there, a thresholdvalue is set for the intensity difference between the interfered lightof the first wavelength p1 and that of the second wavelength p2 todetermine a direction of temperature changes only when an intensitydifference of above the threshold value between the interfered light ofboth wavelengths p1, p2.

For example, when a maximum value of the intensities I1 of theinterfered light of the first wavelength p1 is represented by I1 max,and the intensities of the interfered light of the second wavelength I2′at a time when an intensity I1 of the former has the maximum value I1maxis represented by I2′, a threshold value Ith=(Imax−I2′) is set for thedifferences between the intensities of both interfered light. Algorithmsdifferent from each other are used for |I1-I2|≦Ith and |I1-I2|>Ith so asto correctly determine a direction of temperature changes.

In another method, a direction of temperature changes can be correctlydetermined by not determining a direction of temperature changes betweena point of I1-I2=0 near the crest and trough of a interfered lightwaveform, and the crest and trough of the interfered light waveform, orby reversing the relationship therebetween of FIG. 5C.

Next, algorithms used in the present embodiment will be explained withreference to the flow chart shown in FIG. 6.

In the present embodiment, as described above, a set threshold value isprovided for the intensity differences between the interfered light ofthe first wavelength p1 and that of the second wavelength p2, anddifferent algorithms are used before and after the threshold value todecide a measured temperature.

First, interfered light intensity I1 associated with the firstwavelength p1 of a pulsed laser beam oscillated within 0.5 ms after therise of the pulsed laser beam is stored (Step S1). Then a interferedlight intensity I2 associated with the second wavelength of the pulsedlaser beam oscillated after 0.5 ms from is the rise of the pulsed laserbeam is stored (Step S2).

Then, when a maximum value of the intensities I1 of the interfered lightof the first wavelength p1 is represented by I1max, and the intensitiesof the interfered light of the second wavelength I2′ at a time when anintensity I1 of the former has the maximum value I1max is represented byI2′, a threshold value Ith=(Imax−I2′) is set for the differences betweenthe intensities of both interfered light. It is determined whether anabsolute value |I1-I2| of a difference between the stored interferedlight intensities I1 and I2 in Steps S1 and S2 is larger than thethreshold value Ith (Step S3).

When |I1-I2|≦Ith, the point is near crest and trough of the interferedlight waveform, and a direction of a temperature changes is not decided.The measurement is completed (Step S4).

When |I1-I2|≦Ith, the point is other than a point near the crest andtrough of the interfered light waveform and a direction of temperaturechanges is given based on the relationships of FIG. 5C (Step S5 to S11).

That is, when I1-I2>Ith , and an inclination of a interfered lightwaveform of the second wavelength p2 is positive, a temperature isdetermined to be “Temperature Rising”, and when I1-I2<0, and aninclination of a interfered light waveform of the second wavelength p2is negative, a temperature is determined to be “Temperature Falling”.When I1-I2<0, and an inclination of a interfered light waveform of thesecond wavelength p2 is negative, a temperature is determined to be“Temperature Rising”, and when I1-I2<0, and an inclination of ainterfered light waveform of the second wavelength p2 is positive, atemperature is determined to be “Temperature Falling”.

The result of the measurement according to the present embodiment isshown in FIG. 7. At the lower part of FIG. 7, intensities I1 ofinterfered light of the first wavelength of the laser beam, andintensities I2 of interfered light of the second wavelength of the laserbeam are show. At the upper part of FIG. 7, computed temperature valuesof the semiconductor substrate 6 by the computer 10, and measuredtemperatures read by a thermocouple are shown.

The temperature calculation gives a temperature change amount ΔT(T) anda direction of temperature changes when an intensity I2 of interferedlight of the laser beam of the second wavelength p2 is changed by ¼period. When a temperature is increasing, ΔT is added to a concurrenttemperature, and when a temperature is decreasing, ΔT is subtracted froma concurrent temperature.

As apparent in FIG. 7, it is found that the intensities I1 of theinterfered light of the first wavelength p1 of the laser beam, and theintensities I2 of the interfered light of the second wavelength p2 ofthe laser beam repeat increases and decreases in accordance withtemperature rises and falls, and the computed temperature values andmeasured temperatures read by the thermocouple well agree with eachother.

Thus according to the present embodiment, a semiconductor laser having acharacteristic that an oscillation wavelength of a laser beam emitted bythe semiconductor laser shifts upon rising is used, whereby laser beamsof different wavelengths are easily obtained. Because wavelengthdifferentiation is not necessary for the measurement, no lock-inamplifier is necessary, which makes the device for measuringtemperatures structurally simple and makes the device inexpensive.

Furthermore, a direction of temperature changes can be decided by eachof the emitted pulsed laser beams, whereby temperature change directionscan be accurately provided. The device for measuring temperatures can beof high precision.

Second Embodiment

The device for measuring temperatures according to the second embodimentwill be explained with reference to FIGS. 8 to 11.

The first embodiment uses a semiconductor laser of a III-V compoundsemiconductor, and can realize a temperature measurement of highprecision. But, as described above, semiconductor lasers of III-Vcompound semiconductors have approximately a 1.6 μm oscillationwavelength at longest, and have upper limits totemperatures-to-be-measured of semiconductor wafers, as of silicon,GaAs, etc., having relatively small energy band gaps. Their temperaturemeasuring range is adversely narrow.

To solve this disadvantage, the present embodiment uses a semiconductorlaser of a IV-VI compound semiconductor with a wide wavelength range.That is, IV-VI compound semiconductors, such as, PbSnTe, PbTeS, PbSSe,PbSnSe, etc. having NaCl-type crystal structure having 0.04-0.3 eVenergy band gaps. A semiconductor laser 1 of such a semiconductor canoscillate in a 4-30 μm wavelength range, depending on compositions. Toreceive with high sensitivity laser beams in this wavelength range, aphoto receptor 7 is formed of a IV-VI compound semiconductor of theabove-described structure.

The semiconductor laser of a III-V compound semiconductor used in thefirst embodiment has a characteristic that a wavelength of a pulsedlaser beam shortens by some Angstroms when the pulse rises andthereafter elongates. But the semiconductor laser of a IV-VI compoundsemiconductor used in the present embodiment has the reversecharacteristic that a wavelength of a pulsed laser beam elongates oversome Angstroms when the pulse rises and thereafter shortens.

Accordingly the device for measuring temperatures according to thepresent embodiment has basically the same structure as the device ofFIG. 1, but its determining condition is different from that of thefirst embodiment. The determining condition of the device for measuringtemperatures according to the present embodiment will be explained withreference to FIGS. 8 to 11. FIG. 8 is a graph of relationships betweenmeasured temperatures and interfered light intensities. FIGS. 9A to Care graphs of wavelength changes of pulsed laser beams and changes ofintensities of interfered light associated therewith. FIG. 10A is agraph of intensities of interfered light of laser beams of a firstwavelength p1 and a second wavelength p2. FIG. 10B is a graph oftransient temperatures of the semiconductor substrate 6. FIG. 10C is agraph of relationships between the interfered light and changes oftemperatures of the semiconductor substrate 6.

In the device for measuring temperatures according to the presentembodiment, a silicon substrate as a semiconductor substrate 6 ismounted on a heater 5. When laser beams from the semiconductor laser 1are applied to the semiconductor substrate 6, as shown in FIG. 1, laserbeams reflected from the top and the bottom surfaces of thesemiconductor substrate 6 interfere with each other, and the interferedlight is the reflected light on the semiconductor substrate 6.

While the semiconductor substrate 6 is being heated by the heater 5,laser beams from the semiconductor laser 1 are applied to thesemiconductor substrate 6 via a collimating optical unit 3. Reflectedlight on the semiconductor substrate 6 is received by a photo receptor7, and intensities of the interfered light are analyzed by a computer10.

As a result, a temperature-interfered light intensity characteristicindicated by the solid line in FIG. 8 is obtained. As a temperature ofthe semiconductor substrate 6 is gradually increased, intensities of theinterfered light change into a sine-like curve.

This principle is as follows.

Because the dielectric constant (refractive index) of the semiconductorsubstrate 6 and a thickness thereof increase with a rising temperaturethereof, the effective optical distance inside the semiconductorsubstrate 6 changes. The phase of that portion of the laser beam whichhas traversed through the semiconductor substrate 6 and which has beenreflected from the bottom surface prior to exiting from the top surfaceshifts according to the temperature change. Thus the resultant phaserelationship between the reflected lights from the top surface and thebottom surface changes.

Accordingly an intensity of interfered light of reflected light on thesemiconductor substrate 6 is changed in a sine-like wave by temperaturechanges. A temperature change ΔT(T) [° C.] for one period is calculatedby the following formula when a thickness of the semiconductor substrate6 is represented by L, and a refractive index thereof is represented byn

ΔT=λ/{2nL(α+β)}

where a α=(1/L)×(dL/dT)

β=(1/n)×(dn/dT).

It is difficult to give α and β here. (α+β) is experimentally given.

That is, a temperature change ΔT(T) for one period is given by thefollowing formula, based on a frequency f of an intensity of theinterfered light calculated based on a difference from an experimentalinitial value and a corrected curve of measured temperatures iscalculated by the following fifth order approximation expression.

ΔT(f)=12.278+11.012×f−0.13222×f ²+0.0018399×f ³−1.5803×10⁻⁵ ×f⁴+5.5364×10⁻⁸ ×f ⁵

Thus, a temperature of the semiconductor substrate 6 is decided by atemperature To [° C.] at the start of heating and a number of periods oftemperature changes.

On the other hand, the semiconductor substrate 6 is heated or cooled bythe heater 5, and its temperature rises and falls. To decide atemperature of the semiconductor substrate 6 it is necessary to know adirection of temperature changes thereof. The principle of determining adirection of temperature changes of the semiconductor substrate will beexplained.

Pulsed current of approximately 50 Hz is injected into the semiconductorlaser 1 from a pulse power source 11, and pulsed laser beams of 50 Hzare applied to the semiconductor substrate 6 from the semiconductorlaser 1. The wavelength of the pulsed laser beams from the semiconductorlaser 1 has a characteristic as show in FIG. 9A that the wavelength islong when the pulses rise and shorten by the time when the pulses havetheir normal state.

This characteristic is considered to be due to the fact that because theenergy band gap of the compound semiconductor of the semiconductor laser1 widens as temperature rises due to oscillation, the wavelength of theoscillation light shifts to be shorter.

A first wavelength p1 (=λ−Δλ) of a pulsed laser beam from thesemiconductor laser 1 at the time of rise is longer by Δλ than a secondwavelength p2 the pulsed laser beam in its normal state. As indicated bythe broken line in FIG. 8, the temperature-interfered light intensitycharacteristic showing relationships between intensities of theinterfered light of reflected light of the pulsed laser beam of thefirst wavelength p1 (=λ−Δλ) on the semiconductor substrate 6, andtemperatures has a Φ-phase delay.

Suitable interference can be obtained by a maximum difference Δλ betweenthe first wavelength p1 of a pulsed laser beam oscillated within 0.5 msafter rise of the pulsed laser beam, and the second wavelength p2 (=λ)thereof satisfying the relationship of |Δλ|<λ²/(2nd+λ) with respect to arefractive index n of the semiconductor substrate 6 and a thickness dthereof.

Based on the above, it is seen that while a temperature of thesemiconductor substrate 6 is increasing, with the interfered lightintensity being increased, an interfered light intensity I2 of thesecond wavelength p2 is higher than an interfered light intensity I1 ofthe first shorter wavelength p1, and with an interfered light intensitybeing decreased, oppositely an interfered light intensity I2 of thesecond wavelength p2 is lower than that I1 of the shorter firstwavelength p1.

It is also seen that while a temperature of the semiconductor substrate6 is decreasing, with the interfered light intensity being increased, aninterfered light intensity I2 of the second wavelength p2 is lower thanan interfered light intensity I1 of the first longer wavelength p1, andwith an interfered light intensity being decreased, oppositely aninterfered light intensity I2 of the second wavelength p2 is higher thanthat I1 of the longer first wavelength p1.

With respect to reflected light of a pulsed laser beam shown in FIG. 9A,there are two cases that, as shown in FIG. 9B, the interfered lightintensity is low when the pulsed laser beam rises, and, as shown in FIG.9C, the interfered light intensity is high when the pulsed laser beamrises.

FIG. 9B corresponds to the temperatures T1 with respect to theinterfered light intensity changes of FIG. 8. FIG. 9C corresponds to thetemperatures T2 with respect to the interfered light intensity changesof FIG. 8. FIG. 8 corresponds to the circles and the crosses in FIGS. 9Band C.

Accordingly, it is determined whether a temperature is increasing ordecreasing: by measuring intensities of the interfered light of thereflected light of a pulsed laser beam on the semiconductor substrateimmediately (crosses) after the rise of the pulsed laser beam, and acertain time (circles) after the rise of the pulsed laser beam todetermine whether the interfered light intensity at the rise of thepulsed laser beam is low as in FIG. 9B or is high as in FIG. 9C; and bymeasuring slope of the intensity I1 of interfered light of the firstwavelength p1 or the intensity I2 of interfered light of the secondwavelength p2.

That is, the following is determined with the vicinity of the crest ofthe waveform of the coherent light intensity and the vicinity of thetrough thereof out of consideration.

At the time when the intensity I1 of interfered light of the firstwavelength p1 or the intensity I2 of interfered light of the secondwavelength p2 are increasing, it is determined that when an intensity I1of the interfered light of the first wavelength p1 is higher than thatI2 of the interfered light of the second wavelength (I1>I2) atemperature of the semiconductor substrate 6 is falling, and when anintensity I1 of the interfered light of the first wavelength p1 is lowerthan that I2 of the interfered light of the second wavelength (I1<I2), atemperature of the semiconductor substrate 6 is rising. At the time whenthe intensity I1 of interfered light of the first wavelength p1 or theintensity I2 of interfered light of the second wavelength p2 aredecreasing, it is determined that when an intensity I1 of the interferedlight of the first wavelength p1 is higher than that I2 of theinterfered light of the second wavelength (I1>I2) a temperature of thesemiconductor substrate 6 is rising, and when an intensity I1 of theinterfered light of the first wavelength p1 is higher than that I2 ofthe interfered light of the second wavelength (I1<I2), a temperature ofthe semiconductor substrate 6 is falling.

The method for this determination used in the present embodiment will bespecifically explained. First, pulsed laser beams of a 50 Hz frequencyare applied to the semiconductor substrate 6. Reflected light of theapplied laser beams are received by the photo receptor 7, andintensities of interfered light are stored for the respective pulses. Atthis time, interfered light intensities I1 of the first wavelength p1oscillated within 0.5 msec after the rises of the pulsed laser beams,and interfered light intensities I2 of the second wavelength p2oscillated after 0.5 msec from the rises of the pulsed laser beams asshown in FIGS. 9B and C are extracted and stored, and relationshipsbetween changes of the coherent intensities I1, I2 and time arerecorded.

Based on the graph, for example, a temperature of the semiconductorsubstrate 6 is, by the heater 5, increased in a time (t0-tm) and thendecreased in a time (tm-t2), and relationships between intensities ofthe reflected light on the semiconductor substrate 6 and time aremeasured. The measurement result is as shown in FIG. 10A. In FIG. 10A,the sine-like wave in the solid line indicates interfered lightintensities of the second wavelength p2(λ), and the sine-like wave inthe broken line indicates interfered light intensities of the firstwavelength p1 (=λ−Δλ).

Based on the thus-given interfered light intensities shown in FIG. 10A,temperature changes are given as shown in FIG. 10B.

The above-described physical relationships are opposite near the crestsand troughs of the intensity waveforms of the interfered light. Becauseintensity differences between interfered light of the first wavelengthp1 and that of the second wavelength p2 are small there, a thresholdvalue is set for the intensity difference between the interfered lightof the first wavelength p1 and that of the second wavelength p2 so as todetermine a direction of temperature changes only when an intensitydifference of above the threshold value between the interfered light ofboth wavelengths p1, p2.

For example, when a maximum value of the intensities I1 of theinterfered light of the first wavelength p1 is represented by I1max, andthe intensities of the interfered light of the second wavelength I2′ ata time when an intensity I1 of the former has the maximum value I1max isrepresented by I2′, a threshold value Ith=(Imax−I2′) is set for thedifferences between the intensities of both interfered light. Algorithmsdifferent from each other are used for |I1-I2|≦Ith and |I1-I2|>Ith so asto correctly determine a direction of temperature changes.

In another method, a direction of temperature changes can be correctlydetermined by not determining a direction of temperature changes betweena point of I1-I2=0 near the crest and trough of a interfered lightwaveform, and the crest and trough of the interfered light waveform, orby using another algorithm therebetween.

Next, algorithms used in the present embodiment will be explained withreference to the flow chart shown in FIG. 11.

In the present embodiment, as described above, a set threshold value isprovided for the intensity differences between the interfered light ofthe first wavelength p1 and that of the second wavelength p2, anddifferent algorithms are used before and after the threshold value todecide a measured temperature.

First, interfered light intensity I1 associated with the firstwavelength p1 of a pulsed laser beam oscillated within 0.5 ms after therise of the pulsed laser beam is stored (Step S1). Then a interferedlight intensity I2 associated with the second wavelength of the pulsedlaser beam oscillated after 0.5 ms from the rise of the pulsed laserbeam is stored (Step S2).

Then, when a maximum value of the intensities I1 of the interfered lightof the first wavelength p1 is represented by I1max, and the intensitiesof the interfered light of the second wavelength I2′ at a time when anintensity I1 of the former has the maximum value I1max is represented byI2′, a threshold value Ith=(Imax−I2′) is set for the differences betweenthe intensities of both interfered light. It is determined whether anabsolute value |I1-I2| of a difference between the stored interferedlight intensities I1 and I2 in Steps S1 and S2 is larger than thethreshold value Ith (Step S3).

When |I1-I2|≦Ith, the point is near crest and trough of the interferedlight waveform, and a direction of a temperature change is not decided.The measurement is shown in Step S4.

When |1-I2|>Ith, the point is other than a point near the crest andtrough of the interfered light waveform and a direction of temperaturechanges is given based on the relationships of FIG. 10C (Step S5 toS11).

That is, when I1-I2<0, and an inclination of an interfered lightwaveform of the second wavelength p2 is positive, a temperature isdetermined to be “Temperature Rising”, and when I1-I2>0, and aninclination of a interfered light waveform of the second wavelength p2is negative, a temperature is determined to be “Temperature Falling”.When I1-I2>0, and an inclination of a interfered light waveform of thesecond wavelength p2 is negative, a temperature is determined to be“Temperature Rising”, and when I1-I2>0, and an inclination of ainterfered light waveform of the second wavelength p2 is positive, atemperature is determined to be “Temperature Falling”.

Thus according to the present embodiment, a semiconductor laser having acharacteristic that an oscillation wavelength of a laser beam emitted bythe semiconductor laser shifts upon rising is used, whereby laser beamsof different wavelengths are obtained. As a result, no modulation systemis necessary for shifting an oscillation wavelength of the semiconductorlaser. Because wavelength differentiation is not necessary for themeasurement, no lock-in amplifier is necessary, which makes the devicefor measuring temperatures structurally simple and makes the deviceinexpensive.

Furthermore, a direction of temperature changes can be decided by eachof emitted pulsed laser beams, whereby temperature change directions canbe given in good details. The device for measuring temperatures can beof high precision.

Furthermore, because the laser beams of the semiconductor laser used inthe present embodiment have long wavelengths, even when energy band gapsof semiconductors, such as silicon, GaAs, etc. narrow due to temperaturerises, laser beam absorption amounts do not increase, and temperaturemeasurement of sufficient precision is possible.

Third Embodiment

Then a device for measuring temperatures according to a third embodimentof the present invention will be explained with reference to FIG. 12.FIG. I2 shows a block diagram of the device for measuring temperaturesaccording to the present embodiment. Common members of the presentembodiment with the first embodiment of FIG. 1 are represented by commonreference numerals to simplify their explanation or not to repeat theirexplanation.

In the first embodiment, temperatures are measured by the use ofreflection light on the semiconductor substrate 6, but in the device formeasuring temperatures according to the present embodiment laser beamsapplied to a measurable part of a semiconductor substrate 6. Thesemiconductor substrate 6 has opposed surfaces which are polished toreflect the applied coherent laser beams, and variations in the observedmutually interfering intensities of the reflected light from thepolished surfaces to give the temperature of the object.

A pulse power source 11, a semiconductor laser 1, an optical fiber 2 anda collimating optical unit 3 for applying laser beams to thesemiconductor substrate 6 placed in a chamber 4 are arranged upper asviewed in FIG. 12, and a photo receptor 7, data signal line 8, an A/Dconverting unit 9, and a computer 10 are arranged lower as viewed inFIG. 12.

The chamber 4 has optical windows (not shown) through which pulsed laserbeams are applied to and reflected from the semiconductor substrate 6 inthe chamber 4. The chamber 4 itself may be made of transparent materialwithout the optical windows.

A heater 5 for a semiconductor substrate 6 to be mounted on has a lightpassage hole 5 a formed therethrough. Transmitted light by thesemiconductor substrate 6 is received by the photo receptor 7 throughthe light passage hole 5 a.

Pulsed laser beams emitted by the semiconductor laser 1 are incident onthe semiconductor substrate 6 in the chamber through the optical fiber 1and the collimation optical unit 3. Transmitted light by thesemiconductor substrate 6 is received by the photo receptor 7, and lightreceived signals are supplied to the computer 10 through the data signalline 8.

The principle and operation of the present embodiment are the same asthose of the first embodiment, and their explanation is omitted.

Thus according to the present embodiment, by the use of transmittedlight by a semiconductor substrate to be measured, the device formeasuring temperatures can have a simple structure and can beinexpensive as does the device according to the first embodiment.

Pulsed Laser Beam

In the description so far made above, the term “pulsed laser beam” hasbeen used without definition. The definition of this term will beexplained with reference to FIGS. 13 and 14.

Generally “a pulsed laser beam” means a laser beam whose intensity risesin a very short time and falls in a very short time, and is calledrectangular pulse for its waveform. To be strict with “pulsed laserbeam”, parameters for determining a waveform of the pulsed laser beamare (1) an intensity of the base of a laser beam, (2) a rise time of apulse, (3) a height of a pulse, (4) a duration of the peak of a pulseand (5) a fall time of the pulse are considered. The waveform of apulsed laser beam varies in accordance with values of the parameters.

“A pulsed laser beam” which can be used in the present invention is, inshort, a laser beam whose wavelength, when emitted by the semiconductorlaser, shortens by some Angstroms (the first wavelength p1) when thepulse rises, and thereafter elongates (the second wavelength p2).

Conversely, “A pulsed laser beam” which can be used in the presentinvention is, in short, a laser beam whose wavelength, when emitted bythe semiconductor laser, elongates by some Angstroms (the firstwavelength p1) when the pulse rises, and thereafter shortens (the secondwavelength p2).

A limit of the pulsed laser beam which can be used in the presentinvention was measured by the experimental device of FIG. 13. A pulsepower source 21 is connected to the semiconductor laser 20. A computer22 is connected to the pulse power source 21. The waveform of pulsedcurrent supplied by the pulse power source 21 is controlled by thecomputer 22. Thus laser beams of a required waveform are emitted by thesemiconductor laser 20. As the semiconductor laser 20 NDL5600 (III-Vsemiconductor laser) by NEC was used.

A pulsed laser beam emitted by the semiconductor laser 20 is split intotwo laser beams by a light splitting coupler 23. The split laser beamsare respectively made into parallel ray bundles by their associatedcollimating optical units 24, 25.

Photo receptors 26, 27 respectively receive laser beams emitted by theirassociated collimating optical units 26, 27. The photo receptors wereB4246 by Hamamatsu Photonics. A silicon substrate 28 is placed betweenthe collimating optical unit 24 and the photo receptor 26. Laser beamswhich have passed through the silicon substrate 28 are received by thephoto receptor 26. The silicon substrate 28 is retained at a certaintemperature. Nothing is provided between the other collimating opticalunit 25 and the photo receptor 27, and the laser beam from thecollimating optical unit 25 is received by the photo receptor 27 as itis.

Light received signals received by the photo receptors 26, 27 werecompared and observed by an oscilloscope 29. Light received signals fromthe photo receptor 26 were inputted to an input terminal CN1, and lightreceived signals from a photo receptor 27 were inputted to an inputterminal CN2.

The result of the observation is shown in FIG. 14. In FIGS. 14A to C, alight received signal CN1 from the photo receptor 26 is shown upper, anda light received signal CN2 from the photo receptor 27 is shown lower.When a wavelength of a laser beam changes, an intensity of a lightreceived signal (CN1) of the laser beam which has passed through thesilicon substrate 28 and generated by the light receptor 26 changes, butan intensity of a light received signal (CN2) generated by the lightreceptor 27 does not change. By comparing the light received signalsCN1, CN2 of the light receptors 26, 27 with each other, it can be judgedwhether or not the wavelength of the laser beam had a change.

FIG. 14A shows the pulsed laser beam used in the above-describedembodiments. An intensity of the base of this pulsed laser beam is 0 V;a rising time of the pulse is ? μsec; a height of the pulse is 4V; aduration of the peak of the pulse is 5 msec; and a falling time of thepulse is 80 μsec. In FIG. 14A it is found that a wavelength changeoccurs when the laser beam rises.

FIG. 14B shows a pulsed laser beam with the intensity of the baseincreased. The intensity of this laser beam is 2 V which is a half aheight of the peak. As seen in FIG. 14B, in this case as well, awavelength change occurs when the laser beam rises. Accordingly it isfound that even with the intensity of the base of the laser beam raisedto some extent, wavelength changes occur.

FIG. 14C shows pulsed laser beams of a trapezoidal waveform having alonger rising time of the pulse and a longer falling time thereof. Therising time of the pulse of the laser beams is 2 msec and the fallingtime thereof is 2 msec. As shown in FIG. 14C, in this case as well,wavelength changes take place when the laser beams rise. Thus it isfound that even when a rising time of a pulse of the laser beams is madesome longer, wavelength changes occur.

As evident from the above experiment, the “pulsed laser beam” which canbe used in the present invention includes, in addition to the generallydefined “a laser beam whose intensity rises in a very short time andfalls in a very short time”, a “pulsed laser beam” whose base intensityis higher than 0 V, and a “trapezoidal laser beam” whose pulse risingtime and falling time are longer.

The “pulsed laser beam” which can be used in the present invention issignificant because of sharpness of the pulse rise, and waveforms of thepulse fall are not involved in the wavelength change. Accordinglywaveforms of the laser beam may be rectangular and triangular. The laserbeam may have, in addition, sine-like waveforms and sawtooth waveforms.

Fourth Embodiment

The device for measuring temperatures according to a fourth embodimentof the present invention will be explained with reference to FIGS. 15and 16. FIG. 15 shows a block diagram of the device for measuringtemperatures according to the present embodiment. Common members of thepresent embodiment with the third embodiment of FIG. 12 are representedby common reference numerals not to repeat their explanation or tosimplify their explanation.

The device for measuring temperatures according to the presentinvention, which can incontiguously measure by the use of laser beamstemperatures of a substrate to be measured, has an advantage that, in asemiconductor device fabrication process, a required treatment, such asheat treatments, ion implantation, etching, diffusion, deposition, etc.while monitoring temperatures.

To make a required treatment on a substrate to be measured, it isnecessary that the substrate to be measured is placed in an atmospheredifferent from that in which the device for measuring temperatures ofthe present invention is placed. Accordingly as shown in FIG. 15, laserbeams emitted by a semiconductor laser 1 are applied to a semiconductorsubstrate 6 through an optical window 11 a, and transmitted light by thesemiconductor substrate 6 is incident on a photo receptor 7 through anoptical window 11 b.

The present embodiment solves disadvantages involved in causing laserbeams to pass the semiconductor substrate 4 through the optical window11 a and to exit through the optical window 11 b.

The device for measuring temperatures according to the presentembodiment applies laser beams to the semiconductor substrate 6 andutilizes the fact that intensities of the interfered light of thetransmitted light by the semiconductor substrate 6 change with changesof a temperature of the semiconductor substrate 6 to measuretemperatures of the semiconductor substrate. But when laser beams enterand exit through the optical windows 11 a, 11 b, there is a risk thatinterference may occur due to light reflected inside each of the opticalwindows 11 a, 11 b and due to light reflected between the opticalwindows 11 a, 11 b in addition to light interference of thesemiconductor substrate 6 itself.

There is a risk that light interference of the semiconductor substrate 6itself may be affected by light interference of reflected light insideeach of the optical windows 11 a, 11 b and between the optical windows11 a, 11 b due to thermal expansion of the optical windows themselves 11a, 11 b and thermal expansion of members, e.g., a chamber supporting theoptical windows 11 a, 11 b, which may cause noises of the temperaturemeasurement.

In view of this, in the device for measuring temperatures according tothe present embodiment, both surfaces of the optical windows 11 a, 11 bare slanted to the optical axis of the laser beams so that no lightinterference of reflected light of the laser beams on both surfacestakes place. Accordingly reflected light of the laser beams on the innersurface of the optical window 11 b is deflected, and even when the laserbeams are reflected between the optical windows 11 a, 11 b, thereflected light follows an optical path h2 without causing lightinterference thereof.

Even with the optical windows 11 a, 11 b tilted, transmitted light bythe semiconductor substrate 6 follows an optical path h1 and is incidenton the photo receptor 7 without failure.

FIG. 16A shows a graph of relationships between time and interferedlight intensities obtained by the device for measuring temperaturesaccording to the present embodiment when a temperature is constantlyraised.

As shown in FIG. 16B, with light interference of reflected light betweenthe optical windows 11 a, 11 b being present, troughs and crests ofinterfered light intensities vary. But as shown in FIG. 16A, it is foundthat in the device for measuring temperatures according to the presentembodiment, troughs and crests of interfered light intensities do notvary but are maintained at a constant value.

Thus according to the present embodiment, because no light interferenceof reflected light inside each of the optical windows and between theoptical windows takes place, a level of interfered light intensity doesnot vary due to temperatures. The device for measuring temperatures canbe of higher precision.

The optical windows may be coated by antireflection coating, thereby nolight interference of reflected light inside each of the optical windowsand between the optical windows takes place.

Fifth Embodiment

The device for measuring temperatures according to a fifth embodiment ofthe present invention will be explained with reference to FIG. 17.Common members of the present embodiment with the device for measuringtemperatures according to the fourth embodiment of FIG. 15 arerepresented by common reference numerals not to repeat their explanationor to simplify their explanation.

In the present embodiment, a semiconductor substrate 6 is placed in achamber 4, and laser beams enter the chamber through an optical window11 a and exit through the optical window 11 b. The optical windows 11 a,11 b each have opposed surfaces parallel with each other and are mountedslanted in openings in the chamber 4, so that the surfaces are slantedto the optical axis of the laser beams.

Laser beams reflected from the inside surface of the optical window 11 bis deflected, and even when reflected between the optical windows 11 a,11 b, the reflected light follows an optical path h2 without causinglight interference.

Thus according to the present embodiment, because no light interferenceof reflected light between the optical windows takes place, a level ofinterfered light intensity does not vary due to temperatures. The devicefor measuring temperatures can be of higher precision.

Sixth Embodiment

The device for measuring temperatures according to a sixth embodimentwill be explained with reference to FIG. 18. Common members of thepresent embodiment with the device for measuring temperatures accordingto the fifth embodiment of FIG. 17 are represented by common referencenumerals not to repeat their explanation or to simplify theirexplanation.

In the present embodiment, optical windows 11 a, 11 b the insidesurfaces of which are slanted are used. Such optical windows 11 a, 11 bare disposed in openings in the chamber 4 with the inside surfacesslanted to the optical axis of laser beams and the outside surfaces areflush with the outer circumferential surface of the chamber 4.

Accordingly laser beams reflected from the inside surface of the opticalwindow 11 b are deflected, and even when reflected between the opticalwindows 11 a, 11 b, the reflected light follows an optical path h2without causing light interference. In addition, because the outsidesurfaces of the optical windows 11 a, 11 b are flush with the outercircumferential surface of the chamber 4, the optical windows 11 a, 11 bcan be mounted with high precision.

Thus according to the present embodiment, because no light interferenceof reflected light between the optical windows takes place, a level ofinterfered light intensity does not vary due to temperatures. The devicefor measuring temperatures can be of higher precision.

Seventh Embodiment

Then the device for measuring temperatures according to a seventhembodiment of the present invention will be explained with reference toFIG. 19. Common reference numerals of the present embodiment with thedevice for measuring temperatures according to the fifth embodiment ofFIG. 17 are represented by common reference numerals not to repeat theirexplanation or to simplify their explanation.

The device for measuring temperatures according to the third to thesixth embodiments uses transmitted light for the temperaturemeasurement. But the device for measuring temperatures according to thepresent embodiment uses intensity changes of interfered light ofreflected light on a semiconductor substrate 6 for the temperaturemeasurement.

In the present embodiment, a semiconductor substrate 5 is placed in achamber 4, and laser beams enter the chamber through an optical window12 a and exit through an optical window 12 b. The optical windows 12 a,12 b are disposed in openings formed in the upper surface of the chamber4. The optical windows 12 a, 12 b are mounted so that one surfacethereof 15 flush with the outside circumferential surface of the chamber4 with the other surfaces thereof slanted to the optical axis of laserbeams.

Owing to this arrangement, laser beams reflected from the inside surfaceof the optical window 12 b deflect, so that light interference ofreflected light between the optical windows 12 a, 12 b via thesemiconductor substrate 6 does not occur.

Thus according to the present embodiment, because no light interferenceof reflected light between the optical windows takes place, a level ofinterfered light intensity does not vary due to temperatures. The devicefor measuring temperatures can be of higher precision.

Eighth Embodiment

The device for measuring temperatures according to an eight embodimentof the present invention will be explained with reference to FIGS. 20 to23. FIG. 20 shows a block diagram of the device for measuringtemperatures according to the present embodiment. FIGS. 21 and 22 showthe operational principle of the device for measuring temperaturesaccording to the present embodiment. Common members of the presentembodiment with the device for measuring temperatures of FIG. 1according to the first embodiment are represented by common referencenumerals not to repeat their explanation or to simplify theirexplanation.

As described above, in the conventional device for measuringtemperatures, the temperature measurement cannot be substantially madeuntil interfered light intensities change by at least one period andtheir maximum and minimum values are given. However, if maximum andminimum values of the interfered light intensities are given beforehand,the temperature measurement can be made immediately after staring of themeasurement.

To solve such disadvantage, in the present embodiment, a maximum and aminimum value of interfered light intensities are predicted before atemperature measuring operation by incident angles of laser beams on thesemiconductor substrate 6 are changed so that intensities of theinterfered light shift by at least one period.

In FIG. 21, A1 and A2 represent incident light from a light source. B1and B2 indicate reflected light on the surface of a semiconductorsubstrate 6. C1 and C2 denote reflected light on the back side of thesemiconductor substrate 6. The reflected light B1, B2 on the surface ofthe semiconductor substrate, and the reflected light C1, C2 on the backside of the semiconductor substrate 6 interfere with each othercorresponding to an optical path difference L.

An optical path difference L is expressed by the following formula whena thickness of the semiconductor substrate 6 is represented by d, arefractive index thereof is represented by n, and an incident angle isrepresented by θ,

L=2d(n ²−sin²θ)^(½)

Here when an incident angle of the incident light A1 is θ′(=θ+Δθ), andan incident angle of the incident light A2 is θ, an optical pathdifference L1, L2 of laser beams at the respective incident angles are

L1=2d(n ²−sin²θ′)^(½)

L2=2d(n ²−sin²θ)^(½)

A difference ΔL between the two optical path differences L1, L2 is

 ΔL=L2−L1=2d{(n ²−sin²θ)^(½)−(n ²−sin²θ′)^(½)}.

At least when this difference ΔL is shifted by ½ wavelength (λ/2) ofmeasurement light, interference state is shifted by one period.Accordingly when the difference ΔL is shifted by λ/2 at maximum, amaximum and a minimum coherent intensity can be obtained, and a maximumand a minimum value of interfered light intensities with temperatureschange.

In the above formulas, ΔL is substituted by λ, and θ′ is substituted byθ+Δθ, and the following formula is given.

λ/2≦2d{(n ²−sin²θ)^(½)−(n ²−sin²(θ+Δθ)^(½)}

This formula is rewritten in terms of Δθ, and

Δθ≧sin⁻¹ [n ²−{(n ²−sin²θ)^(½)−λ/4d}²]^(½)−θ

is obtained.

Thus by shifting the incident angle θ of laser beams by Δθ, a maximumand a minimum value of interfered light intensities can be known inadvance.

The device for measuring temperatures according to the presentembodiment can change incident angles of laser beams, based on theabove-described principle. As shown in FIG. 20, a collimating opticalunit 3 is turnable on a position of incidence of laser beams on thesemiconductor substrate 6, so that incident angles f laser beams withrespect to the semiconductor substrate can be changed.

A photo receptor 7 is also turnable on the position of incidence oflaser beams on the semiconductor substrate 6 in synchronization withrotation of the collimating optical unit 3.

The method for measuring temperatures by the device for measuringtemperatures according to the present embodiment will be explained.

First, before the start of a temperature measuring operation, laserbeams emitted by the semiconductor laser 1 are applied to thesemiconductor substrate 6 mounted on a heater 5. The laser beams areapplied with the collimating optical unit 3 first located at theposition indicated by the solid line. Then the collimating optical unit3 is gradually turned without changing an incident position of the laserbeams on the semiconductor substrate 6 to gradually increase an incidentangle θ of the laser beams. The collimating optical unit 3 is turneduntil the incident angle of the laser beams has an increase Δθ. At thistime, the photo receptor 7 is turned on the incident position of thelaser beams to receive reflected light on the semiconductor substrate 6.

The collimating optical unit 3 is turned on the incident position of thelaser beams to increase the incident angle θ of the laser beams. Thenintensities I of interfered light received by the photo receptor 7periodically increase and decrease as shown in FIG. 22. When theincident angle θ is increased by Δθ as described above, intensities ofthe interfered light increase and decrease over at least one period. Amaximum value Imax and a minimum value Imin of the interfered lightintensities can be known. The maximum and the minimum values Imax, Iminare stored. The processing up to here has been made before the start ofthe temperature measuring operation.

When temperatures of the semiconductor substrate 6 are measured, aposition of the collimating optical unit 3 is fixed so that laser beamsare incident at a required incident angle, and the photo receptor 7 isalso fixed at a position where the photo receptor 7 can receivereflected light on the semiconductor substrate 6. Interfered lightintensities are measured with the collimating optical unit 3 and thephoto receptor 7 thus fixed. Because a maximum and a minimum valuesImax, Imin of the interfered light have been already known, it can bepredicted at which position on sine-like waves of a interfered lightintensity curve a measured value will be located. That is, when thetemperature measurement is started, a phase of a current measured valueon a interfered light intensity curve can be seen.

On the other hand, because a temperature change amount ΔT(T) [° C.]corresponding to one-period change of the interfered light intensitycurve is known, when a temperature of the semiconductor substrate 6changes, and a measured value of the interfered light intensity changes,a phase shift amount of the interfered light intensity curve isobtained, with a result that a temperature change amount can beobtained. Thus, a temperature of the semiconductor substrate 6 can bemeasured immediately at the start of an operation of the interferedlight intensity measurement, based on a temperature at the start ofheating the semiconductor substrate and a temperature change amount.

FIG. 23 shows a result of the temperature measurement according to thepresent invention with respect to interfered light intensity changes incomparison with results of that by the conventional method. In FIG. 23 amaximum and minimum values of interfered light intensities given by thetemperature measurement according to the present embodiment. In theconventional measuring method, the temperature measurement cannot bemade until a maximum and a minimum values of the interfered lightintensities are given, and the temperature measurement is enabled 0.85seconds after a start of the measurement. A temperature erroraccordingly occurs. In the method for measuring temperatures accordingto the present embodiment, because a maximum and a minimum value aremeasured in advance, temperature changes can be measured simultaneouslywith the start of a temperature measuring operation.

Thus according to the present embodiment, temperatures can be measuredimmediately at the start of a interfered light intensity measuringoperation without waiting for temperature changes until maximum andminimum interfered light intensities are obtained.

In the device for measuring temperatures shown in FIG. 20, the photoreceptor 7 is displaced corresponding to displacements of thecollimating optical unit 3. As shown in FIG. 24, the photo receptor 7whose photo receiving range is narrow may be substituted with a diodearray 17 having a wide photo receiving range, which makes thedisplacement of the photo receptor unit unnecessary.

Variations of the device for measuring temperatures according to thepresent embodiment will be explained with reference to FIGS. 25 to 27.For simplifying explanation of the variations, FIGS. 25 to 27 show onlyirradiation systems for applying laser beams and light receivingsystems.

A first variation of the device for measuring temperatures according tothe present embodiment is shown in FIGS. 25A and B.

In the present variation, a convex lens 13 whose optical axis isvertical is disposed above a semiconductor substrate 6, an object to bemeasured. The convex lens 13 is so arranged that the focus of the convexlens 13 is in alignment with a measured point of the semiconductorsubstrate 6, so that irradiation light and the reflected light are viathe convex lens 13. An irradiation system is disposed on the left of theconvex lens 13, and the light receiving system is disposed on the rightof the convex lens 13.

In the device for measuring temperatures of FIG. 25A, a collimationoptical unit 3 is disposed upper left of the convex lens 13, and thephoto receptor 7 is disposed on the right of the convex lens 13. When alaser beam is emitted from the collimating optical unit 3 in thedirection of the optical axis of the convex lens 13, the laser beam isrefracted by the convex lens 13 to be incident on the measured point ofthe semiconductor substrate 6. The reflected light on the semiconductorsubstrate 6 is refracted in the optical axial direction by the convexlens 13 to be received by the photo receiver 7.

The collimating optical unit 3 is horizontally displaced left and right,whereby an incident angle with respect to a measured point of thesemiconductor substrate 6 can be changed. At this time, the photoreceptor 7 is also displaced horizontally in synchronization with thecollimating optical unit 3.

In the device for measuring temperatures shown in FIG. 25B, a diodearray 17 with a wide photo receiving range is used in place of the photoreceptor 7 with a narrow light receiving range, and in this case aposition of the light receiving system should not be changed.

A second variation of the device for measuring temperatures according tothe present embodiment is shown in FIGS. 26A and B.

The present variation additionally includes a mirror 14 and a convexlens 15 in the irradiation system, and a convex lens 16 in the photoreceiving system. The mirror 14 is rotary and is arranged so that laserbeams from the collimating optical unit 3 are applied to the rotaryshaft thereof. The convex lens 15 selects a focal distance and alocation so that reflected light on the mirror 14 is always incident ona measured point of a semiconductor substrate 6. The convex lens 16selects a focal distance and a location so that even with differentincident angles, reflected light on the semiconductor substrate isalways received by the photo receptor 7.

In the device for measuring temperatures of FIG. 26A, laser beams fromthe collimating optical unit 3 are reflected from the mirror 14 andrefracted by the convex lens 16 to be received by the photo receptor 7.

The mirror 14 is rotated to thereby change an incident angle withrespect to a measured point of the semiconductor substrate 6. At thistime a reflection angle also changes, but the reflected light isrefracted by the convex mirror 16 so as to always enter the photoreceptor 7.

The device for measuring temperatures of FIG. (26), the photo receptor 7with a narrow light receiving range uses a diode array 17 with a widelight receiving range, whereby a position of the photo receiving systemshould be not be changed.

A third variation of the device for measuring temperatures according tothe present embodiment is shown in FIG. 27A and B.

In the present variation, an irradiation system is disposed on one sideof a semiconductor 6, and a photo receiving system is disposed on theother side. Laser beams emitted by the irradiation system are incidenton the semiconductor substrate 6, and transmitted light by thesemiconductor substrate 6 is received by a photo receiving system.

The device for measuring temperatures of FIG. 27A includes a collimatingoptical unit 3 of an irradiation system at upper left of thesemiconductor substrate 6, and a photo receptor 7 of a light receivingsystem is disposed at lower right of the semiconductor substrate 6.

The collimating optical unit 3 rotates on a measured point of thesemiconductor substrate 6, so that an incident angle of laser beams canbe changed without an incident position of the laser beams on thesemiconductor substrate 6. An ext angle of transmitted light changes inaccordance with an incident angle, but the photo receptor 7 is rotary onthe measured point of the semiconductor substrate, whereby transmittedlight is always received by the photo receptor 7.

The device for measuring temperatures of FIG. 27B includes a diode array17 with a wide photo receiving range in place of the photo receptor 7with a narrow photo receiving range, whereby a position of the lightreceiving system should not be changed.

Ninth Embodiment

A device for measuring temperatures according to a ninth embodiment ofthe present invention will be explained with reference to FIGS. 28 to31. FIG. 28 shows a block diagram of the device for measuringtemperatures according to the present embodiment. Common or similarmembers of the present embodiment with those of the device for measuringtemperatures according to the first embodiment of FIG. 1 are presentedby common reference numerals not to repeat or simplify theirexplanation.

In a case that an object to be measured is a semiconductor substrate 6of silicon, Gabs or others, the semiconductor substrate 6 has thecharacteristic that as a temperature of the semiconductor substraterises, an absorption end wavelength of light shifts to the side of longwavelengths. Due to this characteristic, as a temperature of thesemiconductor substrate rises, and its absorption end wavelength becomesnear to a wavelength of used laser beams, the laser beams are adverselyabsorbed by the semiconductor substrate 6, with results that thetemperature measurement cannot be accurate.

To solve this disadvantage, the present embodiment changes intensitiesof laser beams to be applied to the semiconductor substrate, based ontemperatures of the semiconductor substrate 6, so that even when thesemiconductor substrate 6 has higher temperatures and high laser beamabsorption, the temperature measurement can be accurate.

In the device for measuring temperatures according to the presentembodiment, as shown in FIG. 28, the semiconductor substrate 6, anobject to be measured, is placed in a chamber 4 of quartz. A platinumcircular heater 5 is disposed at the center of the chamber 4. Thesemiconductor substrate is heated by the platinum heater 5.

The semiconductor substrate 6 to be temperature-measured is anapproximately 0.5 mm-thickness silicon substrate. The semiconductorsubstrate 6 may be, in addition to a silicon substrate, a Gabssubstrate, InP substrate or other semiconductor substrate.

A pulse power source 11 is connected to a semiconductor laser 1. Thepulse power source 11 supplies pulsed current of, e.g., 50 Hz to thesemiconductor laser 1, and the semiconductor laser 1 emits pulsed laserbeams. In the present embodiment, the semiconductor laser 1 is NDL5600(wavelength: approximately 1310 nm; output: approximately 0.5 mW) byNEC.

A computer 10 is connected to the pulse power source 11. The computer 10controls intensities of the pulsed current outputted by the pulse powersource 11, so that intensities of the laser beams to be emitted by thesemiconductor laser 1 are controlled.

Pulsed laser beams to be emitted by the semiconductor laser 1 are led tothe collimating optical unit 3 through an optical fiber 2. The pulsedlaser beams are made into parallel bundles of rays by the collimatingoptical unit 3 to be applied to the semiconductor substrate 6 in thechamber 4.

Transmitted light the semiconductor substrate 6 is received by the photoreceptor 7. Received photo signals received by the photo receptor 7 aresupplied to an A/D conversion unit 9 through a data signal line 8. TheA/D conversion unit 9 converts the received photo signals into digitalsignals and supplies the digital signals to the computer 10.

The computer 10 computes intensity changes of interfered light oftransmitted light, based on the received digital photo signals, and,based on is computed results, decides measured temperatures anddirections of temperature changes.

The computer 10 controls intensities of pulsed current supplied by thepulse power source 11, based on measured temperatures to controlintensities of laser beams to be emitted by the semiconductor laser 1.In the present embodiment, as temperatures of the substrate, measuredresults given by the device for measuring temperatures are used.

The measured results given by the device for measuring temperaturesaccording to the present embodiment are shown in FIG. 29.

In a case that the semiconductor substrate 6 is a silicon substrate, andlaser beams of a 1310 nm-wavelength are used, when a temperature of thesemiconductor substrate exceeds approximately 500° C., the siliconsubstrate has higher absorption. So in the present embodiment, as shownin FIG. 29, intensities of laser beams to be emitted by thesemiconductor laser 1 are changed. That is, as shown in FIG. 29, when atemperature T of the semiconductor substrate 6 is below 500° C., anintensity I of laser beams is constant, and when a temperature of thesemiconductor substrate 6 exceeds 500° C., the pulse power source 11 iscontrolled so that intensities I of laser beams are increased inaccordance with the following formula

I=1+(T−500)×0.02.

As a result, even when the silicon substrate has a temperature exceeding500° C. and higher absorption, because of increased intensities of laserbeams, as shown in FIG. 29, intensities of interfered light transmittedby the silicon substrate do not decreased, and the temperaturemeasurement can be accurate. Based on the measured results, temperaturesof the silicon substrate up to approximately 600° C. can be measured.

FIG. 30 shows, as a control, measured results of a case that anintensity of laser beams are not changed. When a substrate temperatureexceeds 500° C., an absorption of the silicon substrate increases, andintensities of interfered light transmitted by the silicon substratedecrease. As a result, a difference between a maximum and a minimumvalues of interfered light becomes small, and the temperaturemeasurement is impossible around 570° C.

In the device for measuring temperatures of FIG. 28, substratetemperatures for controlling the pulse power source 11 are measuredtemperatures given by the device for measuring temperatures but may bemeasured results given by other means. Control temperatures used inheating control by the platinum heater may be used. FIG. 31 shows adevice for measuring temperatures which uses substrate temperatures ofthe semiconductor substrate measured by a thermocouple for the controlof the pulse power source 11. The same members of this device as thedevice for measuring temperatures of FIG. 28 are represented by the samereference numerals not to repeat their explanation.

The device for measuring temperatures of FIG. 31 includes a thermocouple30 which measures substrate temperatures of a semiconductor substrate 6.Detected signals produced by the thermocouple 30 are converted intoanalog temperature measured signals by thermocouple measuring circuit31. Temperature measured signals from the thermocouple measuring circuit31 are converted to digital signals by an A/D conversion unit 9 andsupplied to the computer 10.

The computer 10 controls intensities of pulsed current supplied by apulse power source 11, based on substrate temperatures measured bythermocouple 30 and controls intensities of laser beams from asemiconductor laser 1.

Thus according to the present embodiment, because intensities of laserbeams to be applied to a semiconductor substrate are increased astemperatures of the semiconductor substrate increases, the temperaturemeasurement can be accurate even when the semiconductor substrate hashigh temperatures.

Tenth Embodiment

The device for measuring temperatures according to a tenth embodiment ofthe present invention will be explained with reference to FIGS. 32 to38. FIG. 32 shows a block diagram of the device for measuringtemperatures according to the present embodiment. The same or similarmembers of the present embodiment are represented by the same referencenumerals of the device for measuring temperatures according to the thirdembodiment not to repeat or simplify their explanation.

In the ninth embodiment, the computer 10 controls the pulse power source11 to change intensities of laser beams to be emitted by thesemiconductor laser 1. But it is not easy to keep oscillationintensities of the semiconductor laser 1 stable, based on currentvalues. In the present invention, oscillation intensities of thesemiconductor laser 1 are kept constantly high. Only when a substratetemperature of the semiconductor substrate 6 is low will the constantlyhigh intensity be attenuated.

An attenuation plate 32 is disposed between a collimating optical unit 3and a chamber 4, so that pulsed laser beams made by the collimatingoptical unit 3 into parallel bundles of rays are attenuated to beapplied to the semiconductor substrate 6 in the chamber 4. In thepresent embodiment, attenuation plates 32 with a plurality of differentattenuation degrees are prepared, and the attenuation plates 32 can beautomatically replaced by control of the computer 10. A mechanism forthe displacement of the attenuation plates 32 is not shown.

Pulsed laser beams emitted by the semiconductor laser 1 are fed to thecollimating optical unit 3 through the optical fiber 2. The pulsed laserbeams are made by the collimating optical unit 3 into parallel bundlesof rays, and attenuated by the attenuation plate 32 to be applied to thesemiconductor substrate 6 in the chamber 4.

Transmitted light by the semiconductor substrate 6 are received by aphoto receptor 7. Photo signals received by the photo receptor 7 aresupplied to an A/D conversion unit 9 through a data signal line 8. TheA/D conversion unit 9 converts the received photo signals to digitalsignals, and outputs the digital signals to the computer 10. Based onthe digital received photo signals, the computer calculates intensitychanges of interfered light of the transmitted light, and, based on acomputation result, decide measured temperatures and a direction of thetemperature changes.

The computer 10 selects a kind of the attenuation plates 32. That is,while measured temperatures are low, an attenuation plate 32 with ahigher attenuation degree is used, and as measured temperatures rise,the attenuation plate 32 is replaced sequentially by those 32 with lowerattenuation degrees.

In the case that the semiconductor substrate 6 is a silicon substrate,and laser beams of a 1310 nm-wavelength are used, the silicon substratehas higher absorption as a temperature of the silicon substrate rises.In view of this, in the present embodiment, intensities of laser beamsto be emitted by the semiconductor laser 1 are made so intense thattemperatures of the silicon substrate above 600° C. can be measured, andwhen a substrate temperature is low, intensities of laser beams areattenuated by the attenuation plate 32. When a substrate temperature isbelow 500° C., an attenuation plate A with a 80% attenuation degree isused. When a substrate temperature is between 500 and 600° C., anattenuation plate B with a 60% attenuation degrees is used. When asubstrate temperature is above 600° C., an attenuation plate C with a40% attenuation degree is used. Thus, intensities of laser beams to beapplied to the semiconductor substrate 6 are gradually changed.

Measured results given by the device for measuring temperaturesaccording to the present embodiment are shown in FIG. 33.

When a measured temperature is below 500° C., laser beams attenuated bythe attenuation plate A are applied to the semiconductor substrate 6.While measured temperatures are low, interfered light of sufficientintensities can be obtained, but when measured temperatures are near500° C., the silicon substrate has a higher absorption, and interferedlight transmitted by the silicon substrate 6 lower the intensities. As aresult, as shown in FIG. 33, a difference between a maximum and aminimum values of the interfered light is so small that the temperaturemeasurement is impossible.

When measured temperatures are near 500° C., the attenuation plate 32 isreplaced by the attenuation plate with a smaller attenuation degree, sothat intensities of laser beams to be applied to the silicon substrateare increased. Even when the silicon substrate has higher absorption,interfered light of sufficient intensities can be obtained, and thetemperature measurement can be determined. But when measuredtemperatures are near 600° C., the silicon substrate has higherabsorption, and intensities of interfered light transmitted by thesilicon substrate are lowered. As a result, as shown in FIG. 33, adifference between a maximum and a minimum values of interfered light isso small that the temperature measurement is impossible.

When measured temperatures are 600° C., the attenuation plate 32 isreplaced by the attenuation plate C with a smaller attenuation degree,so that intensities of laser beams to be applied to the siliconsubstrate are increased, and even when the silicon substrate has higherabsorption, interfered light of sufficient intensities can be obtained.The temperature measurement can be determined.

According to the measured results of FIG. 33, temperatures of thesilicon substrate up to around 630° C. can be measured.

FIG. 34 shows, as a control, measured results of a case that intensitiesof laser beams are not changed. When a substrate temperature exceeds500° C., the silicon substrate has higher absorption, and intensities ofinterfered light transmitted by the silicon substrate are lowered. As aresult, a difference between a maximum and minimum values of interferedlight is so small that the temperature measurement is impossible around570° C.

In the device for measuring temperatures of FIG. 32, as substratetemperatures for controlling the pulse power source 11, measuredtemperatures measured by the device for measuring temperatures are used.But measured results given by other means may be used, and controltemperatures used in controlling heating by the heater 5 may be used.

Then variations of the device for measuring temperatures according tothe present embodiment will be explained with reference to FIGS. 35 to38.

A first variation of the device for measuring temperatures according tothe present embodiment is shown in FIG. 35.

An attenuation plate 3 is disposed between a chamber 4 and a photoreceptor 7, so that interfered light transmitted by a semiconductorsubstrate 6 is attenuated to be received by the photo receptor 7. In thepresent variation as well, the attenuation plate 32 is provided byattenuation plates of a plurality of different attenuation degrees, andthe attenuation plates 32 are automatically replaced by control of acomputer 10.

A second variation of the device for measuring temperatures according tothe present embodiment is shown in FIG. 36.

The device for measuring temperatures according to the above-describedembodiment measures temperatures by the use of transmitted light by thesemiconductor substrate 6. In the device for measuring temperaturesaccording to the present variation, the temperature measurement isconducted based on changes of intensities of interfered light ofreflected light of a semiconductor substrate 6. In the case that thetemperature measurement is conducted based on reflected light on thesemiconductor substrate 6, reflected light on the bottom surface of thesemiconductor substrate 6 is adversely absorbed by the semiconductorsubstrate 6 when a temperature of the semiconductor substrate 6increases. The temperature measurement cannot be accurate.

In the present variation, an attenuation plate 32 is disposed between acollimating optical unit 3 and the semiconductor substrate 6, so thatpulsed laser beams made by the collimating optical unit 3 into parallelbundles of rays are attenuated to be applied to the semiconductorsubstrate 6 in a chamber 4. In the present variation as well, theattenuation plate 32 is provided by attenuation plates with a pluralityof different attenuation degrees, and the attenuation plates can beautomatically replaced by control of a computer 10.

A third variation of the device for measuring temperatures according tothe present embodiment is shown in FIG. 37.

In the present variation, an attenuation plate 32 is disposed between asemiconductor substrate 6 and a photo receptor 7, so that interferedlight of reflected light on the semiconductor substrate 6 is attenuatedto be received by the photo receptor 7. In the present variation aswell, the attenuation plate 32 is provided by attenuation plates of aplurality of different attenuation degrees, and the attenuation platescan be automatically replaced by control of a computer 10.

A fourth variation of the device for measuring temperatures according tothe present embodiment is show in FIG. 38.

The device for measuring temperatures according to the present variationmeasures temperatures of semiconductor substrate 6, based on changes ofintensities of interfered light of reflected light on the semiconductorsubstrate 6.

A semiconductor laser 1 and a collimating optical unit 6 are arrangedright above a chamber 4 for a semiconductor substrate 6 to be placed in.Pulsed laser beams made by the collimating optical unit 3 into parallelbundles of rays are incident on an attenuation plate 32 via a beamsplitter 33, and are attenuated there to be applied to the semiconductorsubstrate 6 in the chamber 4.

Reflected light on the semiconductor substrate 6 is again attenuated bythe attenuation plate 32 to be incident on the beam splitter 33. Thelaser beams incident on the beam splitter 33 is split here to bereceived by a photo receptor 7. Photo signals received by the photoreceptor 7 are supplied to a computer 10 through a data signal line 8via an A/D conversion unit 9.

The computer 10 calculates changes of intensities of interfered lightreflected light, based on received digital photo signals supplied to thecomputer 10, and, based on computed results, decides measuredtemperatures and directions of the temperature changes.

The computer 10 replaces an attenuation plate of one kind of attenuationdegree, based on measured temperatures. That is, while measuredtemperatures are low, an attenuation plate 32 with a high attenuation,and as the measured temperatures rise, the attenuation plate 30 isreplaced gradually by attenuation plates 32 with higher attenuationdegrees.

In the present variation, laser beams are passed through the attenuationplate 32 from the collimating optical unit 3 and the photo receptor 7.An attenuation degree of the attenuation plate 32 is half that of theabove-described embodiment.

The attenuation plate 32 may have an attenuation degree as changingcontinuously.

Thus according to the present embodiment, oscillation intensities of thesemiconductor laser are constantly high, and the intensities areattenuated when a substrate temperature of the semiconductor substrateis low, whereby intensities of interfered light of reflected light onthe semiconductor substrate are lowered. As a result, even when thesemiconductor substrate has high temperatures, the temperaturemeasurement can be accurate.

Eleventh Embodiment

The device for measuring temperatures according to an eleventhembodiment of the present invention will be explained with reference toFIGS. 39 to 42. FIG. 39 shows a block diagram of the device formeasuring temperatures according to the present embodiment. FIGS. 40 and41 show a method for measuring temperatures by the device for measuringtemperatures according to the present embodiment.

As shown in FIG. 39, the device for measuring temperatures according tothe present embodiment includes two temperature measuring systems A andB.

Temperature measuring system A measures temperatures of a semiconductorsubstrate 6 carried by a carrier arm 40. The temperature measuringsystem A follows movement of the carrier arm 40 to measure a temperatureof a required measured point of the semiconductor substrate 6. Pulsedlaser beams are made by a collimating optical unit 41 into parallelbundles of rays to be applied to the semiconductor substrate 6.Reflected light on the semiconductor substrate 6 is received by a photoreceptor 42.

The other temperature measuring system B measures temperatures of thesemiconductor substrate 6 mounted on a stage 44 in a chamber 43. Thetemperature measuring system B measures temperatures of the requiredpoint of the semiconductor substrate 6 which has been carried andmounted on the stage 44. Pulsed laser beams are made by the collimatingoptical unit 45 into parallel bundles of rays to be applied to thesemiconductor substrate 6. Reflected light on the semiconductorsubstrate 6 is received by a photo receptor 46.

Thus, in the temperature measuring system A, temperatures of therequired point of the semiconductor substrate 6 are being carried, andin the temperature measuring system B, temperatures of the requiredpoint of the semiconductor substrate 6 are being treated.

In the present embodiment, as shown in FIG. 39B, one laser beam sourceis used commonly by both the temperature measuring system A and thetemperature measuring system B. A semiconductor laser 48 is connected toa pulse power source 47. The pulse power source 47 is connected to acomputer 50. The computer 50 controls pulsed current to be outputted bythe pulse power source 47.

A pulsed laser beam emitted by the semiconductor laser 48 is split intotwo laser beams by an optical split coupler 49. The split laser beamsare supplied respectively to the temperature measuring system A and thetemperature measuring system B.

The split laser beams are made respectively into parallel bundles ofrays by their associated collimating optical units 41, 45 of thetemperature measuring systems A, B. Respective photo receptors 42, 46 ofthe temperature measuring systems 42, 46 receive respective interferedlight reflected light on the semiconductor substrate 6.

Photo signals received by the photo receptors 42, 46 of the temperaturemeasuring systems A, B are supplied to the computer 50. Based on thesupplied photo signals, the computer 50 calculates changes ofintensities of the interfered light of the reflected light, and, basedon results of the computation, decides measured temperatures, and adirection of the temperature changes.

Next, a method for measuring temperatures by the device for measuringtemperatures according to the present embodiment will be explained withreference to FIGS. 40 and 41.

First, the operation of the carrier arm 40 loading the semiconductorsubstrate 6 into the chamber 43 will be explained.

The semiconductor substrate 6 to be carried is mounted on the carrierarm 40. Temperatures of a required point of the semiconductor substrate6 are measured by the temperature measuring system A (FIG. 40A).

Next, the semiconductor substrate 6 is loaded into the chamber 43 by thecarrier arm 40. Temperatures of the semiconductor substrate 6 beingcarrier are measured by the temperature measuring system A (FIG. 40B).

Next, the semiconductor substrate 6 loaded into the chamber 43 by thecarrier arm 40 is transferred onto the stage 44 in the chamber 43. Whenthe semiconductor substrate 6 is mounted on the stage 44 withtemperatures of the semiconductor substrate 6 being continuouslymeasured by the temperature measuring system A, temperatures of thesemiconductor substrate 6 start to be measured by the temperaturemeasuring system B (FIG. 40C). An initial value of the measuredtemperatures by the temperature measuring system b is corrected by themeasured temperatures by the temperature measuring system A. Then thetemperature measurement of the semiconductor substrate 6 is continued bythe temperature measuring system B.

Next, the carrier arm 40 is unloaded out of the chamber 4 (FIG. 40D).Subsequently a required treatment is conducted on the semiconductorsubstrate 6 mounted on the stage 44. During the treatment, temperaturesof the semiconductor substrate 6 are continuously measured by thetemperature measuring system B.

Thus, when the semiconductor substrate 6 is loaded into the chamber 43by the carrier arm 40, temperatures of the required measured point ofthe semiconductor substrate 6 can be measured without interruption.

Next, the operation of unloading the semiconductor substrate 6 out ofthe chamber 43 by the carrier arm 40 will be explained.

First, while the semiconductor substrate 6 is being treated in thechamber 443, temperatures of the required measured point of thesemiconductor substrate 6 on the stage 44 are measured (FIG. 41A).

Then, the semiconductor substrate 6 on the stage 44 is held by thecarrier arm 40. While temperatures of the semiconductor substrate 6 arebeing continuously measured by the temperature measuring system B, uponthe carrier arm 40 holding the semiconductor substrate 6, temperaturesof the semiconductor substrate start to be measured by the temperaturemeasuring system A (FIG. 41 B). An initial value of the measuredtemperatures by the temperature measuring system A is corrected by thetemperatures measured by the temperature measuring system B, and thenthe temperatures of the semiconductor substrate 6 is continuouslymeasured by the temperature measuring system A.

Then, the semiconductor substrate 6 starts to be unloaded by the carrierarm 40 (FIG. 41C), and the semiconductor substrate 6 is unloaded out ofthe chamber 43 (FIG. 41D). Temperatures of the semiconductor substrate 6are continuously measured by the temperature measuring system A.

Thus, when the semiconductor substrate 6 is unloaded out of the chamber43 by the carrier arm 40, temperatures of the required point of thesemiconductor substrate 6 can be continuously measured.

In the temperature measuring device shown in FIGS. 40 and 41, thetemperature measuring system A and the temperature measuring system Bare arranged so as to not interrupt optical paths of the systems A and Bby each other.

With reference to FIG. 42, a case that the device for measuringtemperatures according to the present embodiment is applied to a clusterdevice with a plurality of treatment chambers will be explained.

The cluster device includes three treatment chambers 51, 52, 53. Thesetreatment chambers 51, 52, 53 are adjacent commonly to a vacuum chamber54. A load lock chamber 55 is also adjacent to the vacuum chamber 54. Inthe vacuum chamber 54 there is provided a carrier arm 56 which carries asemiconductor substrate. The semiconductor substrate 6 is carried fromthe outside into the load lock chamber 55 by the carrier arm 56 throughthe load lock chamber 55 to be loaded into and unloaded out of therespective chambers 51, 52, 53.

In the carrier arm 56 there is provided a temperature measuring system Awhich can measure temperatures of a measured point of the semiconductorsubstrate 6 being carried. The temperature measuring system A followsmovement of the carrier arm 56 to always measure temperatures of themeasured point of the semiconductor substrate 6.

A temperature measuring system B is provided in each chamber 51, 52, 53and the load lock chamber 55. These temperature measuring systems Bmeasure temperatures of the measured point of the semiconductorsubstrate 6.

Thus the temperature measuring system A is provided in the carrier arm56, and the temperature measuring systems B are provided in thetreatment chambers 51, 52, 53 and the load lock chamber 55, wherebytemperatures of the semiconductor substrate 6 on the move can becontinuously measured.

When the semiconductor substrate 6 is carried from the outside into theload lock chamber 55, temperatures of the semiconductor substrate 6 aremeasured first by the temperature measuring system B in the load lockchamber 55. Subsequently the semiconductor substrate 6 is unloaded outof the load lock chamber 5, and temperatures of the semiconductorsubstrate 6 are measured by the temperature measuring system A untilloaded into the treatment chambers 51, 52, 53. While the semiconductorsubstrate 6 is being treated in the treatment chambers 51, 52, 53, thetemperature measuring systems B measure temperatures of thesemiconductor substrate 6. While the semiconductor substrate 6 is movingto and from the treatment chambers 51, 52, 53, the temperature measuringsystem A in the carrier arm 56 measures temperatures of thesemiconductor substrate 6. The temperature measuring systems B in theload lock chamber 55 measures temperatures of the semiconductorsubstrate 6 until required treatments on the semiconductor substrate 6are over in the treatment chambers 51, 52, 53, and the semiconductorsubstrate 6 is unloaded out of the load lock chamber 55.

Thus, while the semiconductor substrate is being treated in the clusterdevice, temperatures of the semiconductor substrate are continuouslymeasured.

In the above embodiment, each of the treatment chambers, the carrierarm, and the load lock chamber 56 may have plural temperature measuringsystems.

Twelfth Embodiment

The wavelength measuring device according to a twelfth embodiment of thepresent invention will be explained with reference to FIGS. 43 to 46.

FIG. 43 shows a block diagram of the wavelength measuring deviceaccording to the twelfth embodiment. The wavelength measuring deviceaccording to the twelfth embodiment measures wavelength shifts of laserbeams emitted from a semiconductor laser.

A semiconductor laser 101 whose beams to be measured was, e.g., an NECNDL5600 (InGaAsP phase shift type DFB-DC-PBH laser diode for use in 1310nm-optical fiber communication; approximately 0.5 mW output). Thesemiconductor 1 may be a semiconductor laser with an APC which canoscillate pulsed beams of above 10 Hz.

Laser beams emitted from the semiconductor laser 101 are led to acollimating optical unit 103 through an optical fiber 102. Therespective laser beams are made into parallel rays by the collimatingoptical unit 103 and are applied to a reference substance 106. Awavelength of the laser beams is measured in advance or upon measurementby a spectrometer. Light quantity changes of the laser beams aremeasured by, e.g., a photodiode upon measurement.

The reference substance 106 is a reference for the wavelengthmeasurement. Its refractive index n and thickness L are measured withprecision in advance by an independent method. The reference substance106 may be any substance as long as its accurate refractive index n andthickness L are known and can provide transmitted light of sufficientintensity, but it is preferable that the upper side and the undersidethereof are finished in speculums. For example, the reference substancemay be a semiconductor substrate, as of silicon, GaAs, InP or others.

The reference substance 106 is not essentially a unisubstance but maycomprise, as shown in FIG. 44A, two flat plates 106 a, 106 b spaced fromeach other by a set distance L, and a substance 106 c of a knownrefractive index n loaded between the flat plates 106 a, 106 b. Thesubstance c may be a solid, liquid or gas. The gas may be air.

In addition, the reference substance 106 may comprise, as shown in FIG.44B, thin films 106 d , 106 d in place of the flat plates 106 a, 106 a,and the substance 106 c loaded between the thin films 106 d , 106 d.

The transmitted light which has passed through the reference substance106 are received by a photoreceiver 7. The photoreceiver 7 was aHamamatsu Photonics B246 (Ge photovoltaic device). It is preferred thatthe photoreceiver 7 has a rise time of below 50 μs.

Received photo signals received by the photoreceiver 7 are supplied toan A/D converting unit 109 through a data communication unit 108. TheA/D converting unit 109 converts the received photo signals, which areanalog signals, to a digital signals, and outputs the digital signals toa computer 110.

The computer 110 computes intensity changes of interfered light of thetransmitted light, based on the inputted digital received photo signals,and determines wavelength shifts, based on computed results.

Then the measuring principle of the wavelength measuring deviceaccording to the present embodiment will be explained with reference toFIG. 45. FIG. 45 shows a graph of relationship between wavelengths ofthe laser beams and interfered light intensities.

Interference of a laser beam depends on wavelengths λ thereof, and arefractive index n and a thickness of the reference substance 106. Witha refractive index n and a thickness L of the reference substance madeconstant, as shown in FIG. 45, an intensity I of the interfered lightrepeats increases and decreases between a maximum value Imax and aminimum value Imin in accordance with wavelength shifts λ.

When a wavelength shift amount dλ generated when an interference statechanges by one period is represented by dλ, a refractive index of thereference substance is indicated by n, a thickness of the referencesubstance is denoted by L, and a wavelength of the laser beams beforewavelength shifts is represented by λ, the following formula is realized

dλ=λ²/(2nL+λ)

By detecting a change ΔI of an intensity I of the interfered light, awavelength shift Δλ of the laser beam can be measured in FIG. 45. Whenit is assumed, for example, that an intensity of the interfered lightwhich has been Io before it undergoes a wavelength shift increases byΔI, as shown in FIG. 45, a wavelength decrease of Δλ is measured.

As apparent in FIG. 45, there are present two interference states in oneof which a interfered light intensity I increases as wavelength λincreases, and in the other of which the interfered light intensity Idecreases as wavelength λ increases. Increases and decreases of awavelength cannot be uniquely determined in accordance with increasesand decreases of a interfered light intensity I. An intensity I ofinterfered light undergoes no substantial changes even with wavelengthshifts near a maximum value Imax of the interfered light and a minimumvalue Imin thereof.

In view of this, it is preferred to check in advance, with a interferedlight intensity Io without shifts of a wavelength λ set substantially atthe medium between a maximum value Imax and a minimum value Imin,whether increases of the wavelength λ produce the interference state inwhich the interfered light intensity increases, or the interferencestate in which the interfered light intensity decreases.

To this end, a maximum value Imax and a minimum value Imin, and apresent interference state are made known before measuring wavelengthshifts, by changing other factors for determining conditions of theinterference, preferably changing an interference state by one period.

To change an interference state, it is considered, for example, tochange a refractive index n and a thickness L of the reference substance106, or to change an incident angle of the laser beams to change asubstantial optical path length.

As specific means for changing a refractive index n and a thickness L ofthe reference substance 106, when the reference substance is a siliconsubstrate, changing a temperature of the reference substance 106 iseffective.

It is also possible that the reference substance 106 is formed inwedge-shaped section and is displaced horizontally to change itsthickness L.

Light intensity changes caused by increases of a refractive index n anda thickness L of the reference substance 106 are substantially the sameas shifts of a wavelength of the laser beams to the side of shortwavelengths. Oppositely light intensity changes caused by decreases of arefractive index n and a thickness L of the reference substance 106 aresubstantially the same as shifts of a wavelength of the laser beams tothe side of long wavelengths.

Light intensity changes caused by increases of a substantial opticalpath length caused by changes of an incident angle of the laser beamsare substantially the same as shifts of a wavelength of the laser beamsto the side of the short wavelengths. Oppositely light intensity changescaused by decreases of a substantial optical path length aresubstantially the same as shifts of a wavelength of the laser beams tothe side of long wavelengths.

It is preferable to thus vary interference conditions to obtain anoptimum interference conditions before measuring wavelength shifts, butwhen wavelengths shifts are measured, the interference conditions arekept constant without changes.

FIG. 46 shows a graph of transient interfered light intensity changes inthe case that the reference substance 106 comprises a 0.5 mm-thicknesssilicon substrate, and pulsed laser beams of a 50 msec pulse width areemitted from the semiconductor laser 101 of a 1.3 μm wavelength.Voltages are taken on the vertical axis, and one division is equal to 2V. Time is taken on the horizontal axis, and one division is equal to 1ms.

As shown in FIG. 46, the interfered light intensity is highestimmediately after a pulsed laser beam has risen, then graduallydecreases, and is stable after approximately 10 msec. Accordingly it isfound that a pulsed laser beam emitted from the semiconductor laser 101has a shorter wavelength by approximately 1 angstrom upon rising andthen increases the wavelength. Thus, according to the presentembodiment, wavelength shifts of a laser beam in a period of time asshort as approximately 10 msec can be accurately measured.

As described above, according to the present embodiment, quicklyshifting wavelengths can be measured without allocating a scanning timefor the spectral diffraction.

Thirteenth Embodiment

Next, the wavelength measuring device according to a thirteenthembodiment of the present invention will be explained with reference toFIG. 47. FIG. 47 shows a block diagram of the wavelength measuringdevice according to the thirteenth embodiment. Common members of thethirteenth embodiment with the twelfth embodiment are represented bycommon reference numerals not to repeat their explanation or to lengthentheir explanation.

In the wavelength measuring device according to the twelfth embodiment,transmitted beams by the reference substance 106 are used in measuringwavelengths, but in the wavelength measuring device according to thepresent embodiment, laser beams are applied to one side of a referencesubstance 106, and intensity changes of interfered light of reflectedlight on the side are observed to measure wavelength shifts of thereference substance 106 and wavelength shifts of the reflected light.

In the present embodiment, an irradiation unit including a semiconductorlaser 101, an optical fiber 102, collimating optical unit 103, and aphoto receiving unit including a photo detector 107, a datacommunication unit, a computer 110 are arranged on both sides of thereference substance 106.

Laser beams emitted from the collimating optical unit 103 are incidenton the reference substance 106, and interfered light of reflected lighton the reference substance 106 is received by the photoreceiver 7. Photoreceived signals are inputted to the computer 110 via the datacommunication unit 108. Intensity changes of the interfered light by thephoto receiver 7 are measured for the measurement of wavelength shiftsof the laser beams.

Thus according to the thirteenth embodiment as well as the twelfthembodiment, quickly shifting a wavelength can be measured withoutallocating a scanning time for the spectral diffraction.

The principle and the operation of the thirteenth embodiment are thesame as those of the twelfth embodiment, and are not repeated here.

As described above, according to the thirteenth embodiment, quicklyshifting wavelengths can be measured without allocating a scanning timefor the spectral diffraction in the same way as in the twelfthembodiment.

Fourteenth Embodiment

Then, the wavelength measuring device according to a fourteenthembodiment of the present invention will be explained with reference toFIG. 48. Common members of the fourteenth embodiment with the twelfthembodiment are represented by common reference numeral not to repeattheir explanation or lengthen their explanation.

In the present embodiment, a reference substance 106 is housed in achamber 104, and laser beams enter and exit respectively at an opticalwindows 111 a, 111 b of the chamber 104. The optical windows 111 a, 111b have one surface slanted and provided in openings in the chamber 104so that the slanted surfaces are faced inside, tilted with respect tothe optical axis of the laser beams, and the outer surfaces are flushwith the outside surface of the chamber 104.

Owing to this arrangement, those of the laser beams reflected from theinside surface of the optical window 1 b stray from the optical axis andfollow an optical path h2 even when reflected between the opticalwindows 111 a, 111 b, so that the reflected light causes no lightinterference. In addition, the outside surfaces of the optical windows111 a, 111 b are flush with the outside surface of the chamber 104,which facilitates mounting of the optical windows 111 a, 111 b with highprecision.

Thus according to the fourteenth embodiment, no light interference ofthe reflected light between the optical windows occurs, so that thewavelength measurement can be made with precision without intensitylevel changes of the interfered light. Thus the wavelength measuringdevice according to the fourteenth embodiment can be of higherprecision.

Fifteenth Embodiment

The wavelength measuring device according to a fifteenth embodiment ofthe present invention will be explained with reference to FIG. 49.Common members of the fifteenth embodiment with the thirteenthembodiment of FIG. 47 are represented by common members not to repeattheir explanation or to lengthen their explanation.

In the present embodiment, a reference substance 106 is housed in achamber 104, and laser beams enter and exit at optical windows 112 a,112 b provided in openings formed in the upper side of the chamber 104.The optical windows 112 a, 112 b are mounted with one surface thereofflush with the outer side of the chamber 104, so that the inner surfacesof the optical windows 112 a, 112 b are slanted with respect to theoptical axis of the laser beams.

Owing to this arrangement, those laser beams reflected from the innersurface of the optical window 112 b stray from the optical axis, so thatno optical interference of the reflected light between the opticalwindows occurs.

Thus according to the fifteenth embodiment, no light interference of thereflected light between the optical windows occurs, so that thewavelength measurement can be made with precision without intensitylevel changes of the interfered light. Thus the wavelength measuringdevice according to the fourteenth embodiment can be of higherprecision.

The present invention is not limited to the above-described embodimentand can cove variations and modifications.

In the above-described embodiment, temperatures of an object to bemeasured are measured, but physical quantities other than temperaturesmay be measured as long as their measurement is conducted by the use ofpulsed laser beams each having a first wavelength which is oscillatedimmediately after the rise thereof, and a second wavelength which isoscillated thereafter.

In the above-described embodiments changes of wavelengths of the laserbeams are measured, but wavelength changes can be measured not only onthe laser beams, but also on any light as long as it is coherent.

What is claimed is:
 1. A measuring device utilizing a laser beamirradiated upon an object to be measured to measure a physical quantityof the object, the device comprising: irradiating means for irradiatinga pulsed laser beam, said pulsed laser beam having an intensity which issubstantially constant within each pulse; and measuring means whichmeasure the physical quantity of the object to be measured, saidmeasuring means using a first portion of the laser beam occurringimmediately after a rise of each pulse of the pulsed laser beam andhaving a first wavelength, and a second portion occurring within eachpulse after the first portion and having a second wavelength, said firstand second portions of the laser beam irradiated by the irradiatingmeans.
 2. A measuring device according to claim 1, wherein the measuringmeans measures temperatures of the object to be measured, based onchanges of intensities of first interfered light of reflected light ortransmitted light of the first portion of the laser beam on or by theobject, or changes of intensities of second interfered light ofreflected light or transmitted light of the second portion of the laserbeam on or by the object.
 3. A measuring device according to claim 2,wherein the measuring means judges that the temperatures of the objectare judged to be on increase or decrease, based on a direction of thechanges of intensities of the first or the second interfered light andon a difference between the intensity of the first interfered light andthat of the second interfered light.
 4. A measuring device according toclaim 1, wherein the irradiating means includes a semiconductor laserhaving a characteristic that the first wavelength of the first portionof the laser beam is shorter than the second wavelength of the secondportion of the laser beam, and the measuring device measures thephysical quantity, a temperature, or a direction of changes of atemperature of the object to be measured.
 5. A measuring deviceaccording to claim 4, the measuring means judges that the temperaturesof the object are on increase when the intensities of a first interferedlight are higher than those of a second interfered light at the timethat the intensities of the first interfered light or those of thesecond interfered light are on increase, the temperatures of the objectare on decrease when the intensities of the first interfered light arelower than those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on increase; and the measuring means judges thatthe temperatures of the object are on decrease when the intensities ofthe first interfered light are higher than those of the secondinterfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are ondecrease, the temperatures of the object are on increase when theintensities of the first interfered light are lower than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are ondecrease.
 6. A measuring device according to claim 1, wherein theirradiating means includes a semiconductor laser having a characteristicthat the first wavelength is longer than the second wavelength, and themeasuring device measures a physical quantity, a temperature, or adirection of changes of a temperature of the object to be measured.
 7. Ameasuring device according to claim 6, wherein the measuring meansjudges that the temperatures of the object are on decrease when theintensities of a first interfered light are higher than those of asecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are onincrease, the temperatures of the object are on increase when theintensities of the first interfered light are lower than those of thesecond interfered light at the time that the intensities of the firstinterfered light or those of the second interfered light are onincrease; and the measuring means judges that the temperatures of theobject are on increase when the intensities of the first interferedlight are higher than those of the second interfered light at the timethat the intensities of the first interfered light or those of thesecond interfered light are on decrease, the temperatures of the objectare on decrease when the intensities of the first interfered light arelower than those of the second interfered light at the time that theintensities of the first interfered light or those of the secondinterfered light are on decrease.
 8. A measuring device according toclaim 1, wherein the irradiating means is so arranged that when thesecond wavelength of the second interfered light is represented by λ, athickness of the object to be measured is represented by d, and arefractive index of the object to be measured is represented by n, adifference Δλ between the first wavelength of the first interfered lightand the second wavelength of the second interfered light satisfies|Δλ|<λ²/(2nd+λ).
 9. A measuring device according to claim 1, wherein theirradiating means changes the intensity of the laser beam based ontemperatures of the object to be measured.
 10. A measuring deviceaccording to claim 9, wherein the irradiating means maintains orincreases the intensity of the laser beam when the temperature of theobject is rising, and maintains or decreases the intensity of the laserbeam when the temperature is falling.
 11. A measuring device accordingto claim 9, wherein the measuring device includes means for decreasingthe intensity of the laser beam, and the intensity of the laser beam isdecreased based on the temperature of the object to be measured.
 12. Ameasuring device according to claim 1, further comprising a containerfor the object to be placed in, the container having optical windows onwhich light to be irradiated upon the object to be measured and whichexit reflected light or transmitted light of the irradiated light on orby surfaces thereof, and at least one surface of the optical windowsbeing slanted with respect to the optical axis of the laser beams sothat no interference of reflected light inside each of the opticalwindows and between the optical windows takes place.